ZURICH (AP) — It was in the final minutes of a June 2011 soccer game between Nigeria and Argentina when the little green flags on computer screens in London started to change color.
Nigeria was leading 4-0 in the exhibition match of little significance, and more and more money was being laid down around the world on the possibility that one of the teams would score another goal before the game was over. Monitors hired by the soccer governing body FIFA to detect deviations from expected betting patterns — helped by computer algorithms — spotted something fishy.
The game's 90 minutes of regular time ended without another goal. Referee Ibrahim Chaibou ordered additional time added to the clock — normal in most soccer games to make up for stoppages in play throughout the contest for injuries or other minor delays. He added six minutes — a substantial amount for such a minor game.
When that time ran out, the game continued, with the score still at 4-0. The clock reached 98 minutes.
That's when Chaibou called Nigerian defender Efe Ambrose for touching the ball with his hand — an infraction that brought a penalty kick for Argentina.
EDITOR'S NOTE: This story is part of a months-long, multiformat AP examination of how organized crime is corrupting soccer through match-fixing, running this week.
Ambrose couldn't believe it. Video replays showed the ball touching him halfway up his thigh, with his arm behind his back and his hand nowhere near the ball. The replay also suggested that Chaibou had a clear view of the play.
But the referee pointed straight to the spot and patted his elbow twice as if to confirm his call beyond any doubt. Nigerian players crowded around him, one even laughing in bemusement. Argentina scored the penalty, and the game ended 4-1.
Within days, both FIFA and the Nigerian Football Association announced they would look into the possibility that the match had been fixed.
The world's most popular sport is under sustained attack from criminal gangs that corrupt players, referees and soccer officials into rigging matches — determining in advance the result of a game, or how many goals are scored and when.
The profits from betting on fixed games are so vast that at least two organized crime groups have recently switched from drug trafficking to match-fixing, Interpol chief Ron Noble told The Associated Press. Sportradar, a European company that monitors worldwide betting, says up to 300 games a year could be fixed in Europe alone.
Referees are tempting targets for match-fixers because their decisions can significantly alter a game's outcome. They also make bad calls all the time for reasons that have nothing to do with corruption, so any investigation centers on collaborating evidence, such as unusual spikes in betting or confessions from people paid off by crime gangs.
Chaibou, a slim, bald 46-year-old from the West African country of Niger, is one of football's most-investigated international referees. Matches in which he officiated have been investigated by FIFA, the Nigerian Football Association and the South African Football Association. At least five of his matches have been flagged as suspicious by betting monitoring companies, an action that usually prompts FIFA and national football organizations to look into the possibility that it was fixed.
None of those have resulted in formal charges or sanctions, and Chaibou denies any connection to match-fixing. He says he has retired from soccer and now works in Niger's military.
In a telephone interview from his home in Niger's capital of Niamey, Chaibou acknowledged that soccer authorities have been questioning him about matches he officiated, including the Argentina-Nigeria game.
"The people from FIFA have already asked me. ... They asked me all the questions about this goal. They asked around everywhere, a bit to everyone," he said. "I judged it to be a penalty, so I gave a penalty ... to make everyone happy. That's it."
It wasn't the first time Chaibou had officiated a suspicious match. In 2010 and 2011, he was the referee at five exhibition matches between national teams in Africa, the Middle East and South America that were flagged by a leading betting monitoring company as potentially fixed, according to confidential company reports seen by the AP.
Before the FIFA-South African investigation was completed, Chaibou turned 45 and was forced to retire from FIFA's approved international referee list in December 2011 due to age limits. That also automatically canceled the investigation, since FIFA investigates only active referees, and no sanctions were issued.
"Ibrahim Chaibou left football before FIFA could launch any potential disciplinary action against him," the FIFA media department said in an email, adding that Chaibou "could of course be investigated again, should he return to soccer."
Chris Eaton, a former security chief for FIFA, said the governing body's investigators tried and failed to question Chaibou in the six months before his retirement, a development he called disappointing.
"People who have serious allegations of corruption against them ought to be properly investigated, if only to clear them of the allegations or confirm them," he said.
FIFA, which has pledged a zero-tolerance fight against corruption in soccer, manages a list of about 2,000 elite referees and linesmen who are qualified to handle national team and international club matches. Each year, FIFA's 209 national associations propose candidates between the ages of 25 and 45 who have worked in top-tier matches for at least two years. A referees committee has veto power over the nominations.
To be accepted, referees must have achieved acceptable grades in domestic matches and must pass FIFA-approved fitness and medical tests. They cannot hold an official position at any soccer club. Successful candidates get to wear a FIFA crest on their shirt.
In 2010, Chaibou was hired for matches in South Africa, Bahrain, Bolivia and Ecuador and small tournaments played in Egypt.
Many of them were organized by Wilson Raj Perumal, who has been convicted of match-fixing in Finland for Asian crime syndicates, and wrote about the fixes in a series of jailhouse letters to a Singaporean journalist in which he linked Chaibou to suspicious matches in South America. After serving his sentence and being released, Perumal has been helping law enforcement authorities in Hungary and Italy uncover rigged games. He has given testimony that is considered a major breakthrough in uncovering match-fixing in Europe.
Perumal's company hired Chaibou to officiate at two games in 2010 — South Africa-Guatemala and Bahrain-Togo. The first was investigated by FIFA and the South African soccer federation; the second involved a team of impostors. Eaton said that when Perumal was arrested in Finland in February 2011, he had Chaibou's number on his phone.
Chaibou also officiated two other games in South America — Bolivia-Venezuela and Ecuador-Venezuela — in October and November 2010, respectively, according to documents provided by FIFA. Both of those matches raised flags with betting monitors, according to confidential betting reports. In a letter written from jail, Perumal claimed the Bolivia match was "sold to an investor in China" — a euphemism for Asian crime gangs.
In Ecuador, the home team won 4-1, helped by penalties scored by both teams that were "similarly questionable," according to a confidential betting monitoring report.
When asked by the AP whether he knew Perumal, Chaibou became combative.
"You already asked me this question last time. I told you I don't know him. I don't know him!" he said, his voice rising. "I told you I don't know these people."
In two previous calls to Chaibou, AP had not mentioned the name.
In 2010, Bahrain's soccer federation hired Perumal to arrange an exhibition match between its national team and that of Togo.
But when the match was played in the Bahraini capital of Manama in September of that year, the rag-tag team from Togo contained none of the players from its national squad. Its coach was not that of the Togolese team, but rather Tchanile Bana, who was serving a two-year ban by Togo for a previous soccer scam.
Bahrain won 3-0, but its coach still complained angrily after the game; the score would have been even more lopsided if officials had not nullified several Bahraini goals on offside calls.
The referee was Chaibou.
From his prison cell in Finland, Perumal wrote to a Singaporean journalist that "Ibrahim Chaibo (sic) was put in charge of this match to keep the score as low as possible."
Perumal said he wagered "against the current" of other Singapore bettors who knew about his ties to the Togo game and who put down money on the Africans losing by a lot.
Chaibou denied that anyone influenced the match: "These are refereeing decisions. That's all."
Asked whether Perumal had dictated the outcome, Chaibou hung up.
He did not answer further calls from the AP.
FIFA did not investigate because there was no formal complaint by either national federation about the match, which has become notorious in the soccer world for hurting the image of international exhibitions.
Two weeks before the 2010 World Cup in South Africa, Chaibou refereed another game that caught the eye of journalists as well as betting monitors, who watch information from 300 betting agencies.
The South African Football Association had hired the Football4U agency, later linked to Perumal, to arrange a string of exhibitions, including a May 31 match against Guatemala. Chaibou was the referee.
The monitoring systems noted suspiciously strong pre-match backing for a South African victory, despite the fact the team was resting several regulars, and for at least three goals to be scored in the game, according to a confidential monitoring report.
South Africa won 5-0, with two of the goals coming from the three handball penalties awarded by Chaibou. The first was called on defender Gustavo Cabrera, who replays showed was clearly standing outside the penalty area. Guatemala was awarded a penalty in the 50th minute when South Africa defender Lucas Thwala blocked a shot with his chest; the South African goalkeeper made the save on the ensuing penalty kick. Chaibou gave South Africa another penalty kick four minutes later, and the team scored.
The South African Football Association immediately became suspicious and dropped all of Perumal's referees, canceling Chaibou's plans to officiate its next game against Denmark.
Chaibou denied that anyone had pressured him to influence the outcome of the match.
On Dec. 15, 2012, the South African Football Association announced that a FIFA report found "compelling evidence" that one or more of its games was fixed in 2010. It said referees hired by Perumal were thought to have manipulated its exhibition games before the World Cup for betting purposes, adding that no players were thought to have been involved. It did not name the referees. It has not imposed sanctions but the investigation continues.
Eaton, who has since joined the Qatari-funded International Centre for Sport Security, said he will continue to investigate Chaibou. It is his responsibility, he said, "to protect all sport from the influence of criminals infiltrating sport and corrupting individuals within sport."
"The allegations against referee Chaibou mean he is a person of interest to the ICSS Integrity Unit and its investigators," Eaton said.
Chaibou insists he has never fixed a match.
"It's got nothing to do with me," he said. "I refereed my matches and went home peacefully. End of story."
Sports Writer John Leicester in Paris and Assistant Europe Editor Sheila Norman-Culp in London contributed to this story.
Follow Graham Dunbar on Twitter at gdunbarap(at)twitter.com