SKIPPACK TWP., Pennsylvania (WPVI) -- Five people were injured Thursday morning in an accident during a training exercise at a prison in Montgomery County.
The accident at the SCI Phoenix prison in Skippack Township occurred shortly before 10 a.m. The training session was being conducted by the FBI's Philadelphia field office and those in attendance included representatives from several state, county and local law enforcement agencies.
According to authorities, three members of the Montgomery County Sheriff's Office Bomb Squad, a Pennsylvania State Police trooper and an FBI Philadelphia agent were injured when an explosive device went off.
All have been transported to area hospitals for treatment. Some injuries were said to be very serious.
"Staff from the Montgomery County Bomb Squad were installing an explosive device for a later class when it prematurely exploded," according to a statement from a prison spokesperson.
One of the sheriff's deputies was taken to Penn Presbyterian Hospital where fellow deputies were waiting outside Thursday night.
Department of Corrections staff was not involved in the training.
Jackie Hickey is a retired bomb technician for the Los Angeles Police Department and part of the FBI Joint Terrorism Task Force. She says reconstructing a car bombing is something routinely done for post-blast investigation training
"Training accidents don't usually occur, but the investigators will figure out how this happened," she said. "I worry for the techs that were injured. There's a lot of damage that occurs in an explosion, especially a vehicle. It has metal glass and a lot of debris that will come from that explosion."
Video from Chopper 6 showed a large police presence and two medical helicopters at the scene.
A charred car was also seen in a field on the prison grounds.
Anthony May, a former ATF explosive enforcement officer bomb technician, says by the looks of the charred vehicle, it appears the charge may not have been contained.
"The entire roof of the car will come off, the doors will blow open, and sometimes depending on the charge, we use all we have left in the frame of the vehicle. It appears that this was not that type of a device, not well contained or that they were just in set up procedures when this accident occurred."
No further details on the accident have been released.
The FBI and Pennsylvania State Police will jointly investigate the cause of the detonation.