LOS ANGELES (AP) — Authorities are looking into whether grenades recovered from a Santa Monica apartment complex were the cause of an explosion last week at a Los Angeles County Sheriff’s Department training facility that killed three members of its arson and explosives unit.

The three members had assisted local police following the discovery on Thursday of grenades at an apartment complex in Santa Monica.

Meanwhile, as detectives chase leads into the origins of the grenades following the deadly blast at the Biscailuz Training Facility, investigators served a search warrant Monday morning at an address in the Marina del Rey neighborhood. The department didn’t say what, if anything, was found.

It was not known whether the grenades had any connection to the military. The Los Angeles County Sheriff’s Department spokesperson Nicole Nishida said investigators were looking at all leads.

The deaths early Friday marked the department’s worst loss of life in a single incident since 1857, when four officers were killed by gunfire, Los Angeles County Sheriff Robert Luna said.

The department identified the deputies who died as Detective Joshua Kelley-Eklund, Detective Victor Lemus and Detective William Osborn. They served 19, 22 and 33 years in the department respectively, Luna said.

Luna said Friday that it took more than four hours to render the scene safe and the deaths were being investigated by the department’s homicide detectives, with the assistance of the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives. No one else was injured, he said.

The sheriff said the arson and explosives team undergoes in-depth training and responds to more than 1,000 calls a year.