LOS ANGELES (AP) — Two Los Angeles County sheriff’s deputies were seriously hurt Tuesday after a fire broke out at a training facility north of Los Angeles.

The deputies were listed in critical condition after being injured at the training center in Castaic, a community roughly 35 miles (55 kilometers) northwest of downtown Los Angeles.

No other details on the injuries were immediately released.

It was unclear how many total people were injured and what caused the blaze. Firefighters, using water cannons, fought the fire for hours. A KTLA helicopter over the scene showed firefighters spraying water into the smoking rear of a parked semitrailer.

The fire happened at about 9:30 a.m. at the facility located on a sprawling campus that also houses the Pitchess Detention Center, a county jail, the sheriff’s department said.

About 10 minutes later, firefighters were dispatched to the scene and “live rounds” at the training center were making it challenging to fight the blaze, said Fred Fielding, a spokesperson for the Los Angeles County Fire Department.

The sheriff’s department is still trying to determine the cause, spokesperson Nicole Nishida said.

The fire department initially said four deputies were taken to the hospital. The sheriff’s department later said two deputies were transported to the hospital. Patrick Moody, a spokesperson for Henry Mayo Newhall Hospital said two deputies there were listed in critical condition.