Three Los Angeles County sheriff’s deputies assigned to the arson explosives detail were killed in an explosion at a law enforcement training facility.

Senior law enforcement officials said the LASD bomb squad responded to a garage in Santa Monica yesterday, where at least one grenade was found. It was transported to the training facility, where the deputies were working to render it safe,

It was not immediately clear what caused the blast at the Los Angeles County Sheriff’s Department’s Biscailuz Training Academy center. No one else was injured, officials said.