Sixteen members of the Orange County Sheriff’s Department SWAT team were injured Wednesday afternoon in an explosion at an FBI training facility in Irvine, according to authorities.

The explosion occurred around 1 p.m. in a small building at the Jerry Crowe Regional Tactical Training Facility, according to Sheriff’s Sgt. Frank Gonzalez.

The SWAT team was conducting its annual joint training with a bomb squad at the time, he said. The FBI wasn’t involved and had lent them the facility for the exercise.

Fifteen people were taken to hospitals. One person sustained a leg injury that will require surgery but is not life-threatening. Two others have superficial wounds, including back and leg injuries. The 13 other people went to the hospital as a precaution because of dizziness and ringing in their ears, but many have already been discharged.

The FBI training facility is on the grounds of the former El Toro Marine base.

Gonzalez didn’t have more information about what could have caused the explosion.

“That’s gonna be part of the investigation,” he said. “Trying to figure out exactly why that happened.”

The Sheriff’s Department and the FBI are investigating the incident.

Times staff writer Richard Winton contributed to this article.