Three people were killed Friday in an explosion at the arson and explosives unit at Biscailuz Center, the Los Angeles County Sheriff’s Department’s main training academy in East L.A., authorities said. One other person was injured.

Few details have been released about what caused the blast, which occurred during a training-related operation. The Los Angeles County Sheriff’s Department said it is cooperating with investigators, and no foul play is currently suspected.

The explosion is the latest in a series of deadly incidents tied to LASD training sites across the county. At least 15 people have died during department training activities since 2016, according to records reviewed by the Los Angeles Times. The incidents include medical emergencies, tactical mishaps, and another explosion in 2020 at the department’s mobile range facility in Castaic, which seriously injured a bomb technician.

Some of the deaths occurred during physically demanding drills. In one case, a recruit suffered a heart attack after a long training run. In others, causes were not made public, and family members have said they received little information from the department.

The sheriff’s department operates more than two dozen specialized facilities for firearms, bomb squads, K-9 units, and emergency driving. Oversight and reporting standards vary, and many of the incidents have not been widely disclosed.

In the wake of Friday’s explosion, the Los Angeles County Board of Supervisors has called for a full review of training site safety and transparency. Officials have not yet released the names of those killed.