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

The explosion was reported about 7:30 a.m. at the Biscailuz Training Facility, Los Angeles County Sheriff’s Department spokesperson Nicole Nishida said. It was not immediately known what caused the explosion or what the deputies were doing at the time.

A Friday blast at a Los Angeles County Sheriff’s Department training facility killed three members of its arson and explosives unit, marking one of the department's worst losses of life from a single incident,