An explosion at a Los Angeles County Sheriff's Department training facility killed three deputies with 74 years of combined service, prompting investigations by the FBI and ATF.

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,

An explosion that killed three Los Angeles County Sheriff's deputies occurred one day after they responded to a call involving explosives at a Santa Monica complex.

Arson and Explosives detectives believed two grenades found at the complex were inert, but took them to be destroyed and rendered safe.

The department said it appears the detectives were moving explosives on a cart in the training center's parking lot when the blast occurred.

Three veteran Los Angeles County Sheriff’s Department members assigned to the agency’s arson and explosives detail were killed Friday morning by an explosion at a department training facility, according to Sheriff Robert Luna.

Officials served a search warrant in Marina del Rey on Tuesday as they continue to investigate a deadly explosion that killed three sheriff’s deputies.