CHICAGO (AP) — A federal agency said Tuesday it is investigating the injury of a fire-blowing stilt-walker who was burned during a dress rehearsal at the Lyric Opera of Chicago.

A compliance officer from the Occupational Safety and Health Administration has already visited the opera, said spokesman Scott Allen. The agency will interview witnesses, performers and employees to determine exactly how the accident happened and whether any safety regulations were violated.

Wesley Daniel suffered second-degree burns around his mouth during a dress rehearsal Monday for "Die Meistersinger von Nuernberg." Journalists invited to watch the rehearsal said the 24-year-old performer had to swig flammable liquid and spit it onto a torch he was holding. They described him staggering off stage and falling to the floor.

Daniel's father told the Lyric's deputy general director, Drew Landmesser, on Tuesday that although his son's mouth was burned, his throat and lungs are fine, the opera said. Daniel was expected to be discharged from Loyola University Medical Center on Thursday.

"The news from Wesley's dad was that everyone seemed to be doing just fine and was relieved," Landmesser said.

The Lyric said the fire-blowing stunt had been approved by the Chicago Fire Department, but it has now been removed from the production. Landmesser said the opera is cooperating with OSHA.

Daniel was wearing a flameproof costume and mask during the dress rehearsal, Lyric spokeswoman Magda Krance said. A staff member used a fire extinguisher to put out flames onstage, according to witnesses and journalists present.