Players from the Essendon football club may have been duped into testing a banned drug, and police could be called in to investigate, reports say.

A company which produces AOD-9604 has described trials with `professional footballers' as proof of the drug's attributes, saying it adds 'muscle mass', aids recovery and increases 'exercise tolerance', Fairfax Media reported on Saturday.

The trial comments were made in a December 2012 patent application from Metabolic Pharmaceuticals, which is based in Melbourne.

The application does not specify which club the footballers are from but Fairfax reports the Australian Sports Anti-Doping Authority (ASADA) believes them to be from Essendon.

Essendon representatives deny any knowledge of such trials for the drug, which is banned by the World Anti-Doping Agency.

The patent claims come only months after Essendon ended its supplements program, having sacked its instigator Stephen Danks.

The program was found to have involved several players using AOD-9604, at amounts and frequencies much greater than its clinical trials.

Although they signed consent forms agreeing to take the drug, they were reportedly not aware that its effects were being tested.

When asked about Metabolic's drug testing of players, Acting Essendon chief executive Ray Gunston said the club was 'extremely concerned about this allegation', Fairfax reported.

"We will be sending this documentation on to both the AFL and ASADA and will be seeking their advice," he said.

"It would be very concerning to the club if any of our players, or information about our players, were used in this way."

Players could file both criminal and civil charges, if they are found to have been trialled without their knowledge.