Three members of the arson and explosives unit of the Los Angeles County Sheriff’s Department were killed Friday in a blast at the department's training facility. It was not immediately clear what they were doing when the explosion happened in a parking lot at the Biscailuz Training Facility or what caused it.

An explosion at a Los Angeles County Sheriff's Department training facility on Friday killed three deputies, the sheriff said.

Federal agents are investigating, but authorities describe it as "an isolated incident" with no further threat to the public.