A grenade is missing from the scene of an explosion at a Los Angeles County Sheriff’s Department training facility that killed three members of its arson and explosives unit, authorities said Friday. At the time of the July 18 blast, the veteran deputies were working on two grenades that had been taken into custody by authorities. One of the grenades detonated, and the other is unaccounted for, Sheriff Robert Luna said, according to the Bureau of Alcohol, Tobacco and Firearms. The agency is investigating the explosion and is expected to publish a final report in 45 days. Luna said authorities X-rayed special enforcement bureau vehicles, searched all around the blast area and examined office spaces and even the gym and haven’t found it. “You get the drift. We have looked at everything out there that we possibly could,” he said, adding that no one from the public has had access to the area. 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, 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.