Ammunition heard going off inside mobile trailer at the gun range of the Pitchess Detention Center kept firefighters responding to a fire at a safe distance.

Shortly after noon, firefighters responded to reports of a structure fire on the 29300 block of The Old Road at Biscailuz Drive.

“This was for a mobile gun-range trailer,” said Brian Stevens, spokesman for the Los Angeles County Fire Department.

Firefighters who approached the site of the burning trailer were told by their dispatchers to keep a safe distance from the trailer. The 40-foot tractor trailer where the fire broke out was used to store ammunition, Stevens said.

When asked about the ammunition exploding inside it, he said: “They can have the potential to go through the trailer, but lacking direction, as with the barrel of a gun, the projectiles will not land as far.”

Firefighters maintaining a safe distance from the trailer continually tried to cool its exterior.

“We are actively putting it out,” Stevens said. “I’m looking at images of two of our guys on an elevated roof applying water to cool the trailer.”

Fire officials at some point were expected to tell firefighters when it’s safe to approach the trailer, he said.

Meanwhile, jail facilities at the North County Correctional Facility remain on lockdown, said Deputy Joanna Warren, spokeswoman for the Los Angeles County Sheriff’s Department.

“We put in place a mandatory lockdown for safety purposes,” she said.