A grenade remains missing as the investigation continues into the deaths of three L.A. County deputies who were killed when military-style grenades exploded at a training facility.

The blast occurred on July 18 at the Biscailuz Regional Training Center at around 7:30 a.m.

The fallen deputies were identified as Detective Joshua Kelley-Eklund, Detective Victor Lemus, and Detective William Osborn. All three were assigned to the LASD Special Enforcement Bureau’s Arson Explosives Detail.

A preliminary investigation indicated the explosives may have been connected to an operation that took place a day before the blast in Santa Monica.

Deputies, including the three who died, were called to an apartment building to assist Santa Monica Police officers with an investigation into explosive devices found in a storage unit in the building’s underground parking garage.

A woman cleaning out the storage bin spotted the devices and called authorities. Neighbors believe it was likely left behind by a former tenant who was a previous member of the U.S. military and had moved out of the complex around five years ago.  

The two military-style grenades, which were believed to be stolen, were x-rayed at the scene and deemed inert.

The July 18 explosion reportedly happened when one of the grenades was being cut in half as part of a training exercise to examine what was inside. 

On Friday, L.A. County Sheriff Robert Luna said detectives determined one of the two grenades detonated on July 18, while the second grenade is currently unaccounted for.

“An extensive search of the training facility was conducted, including x-raying all special enforcement bureau vehicles, a grid search from the blast site and the surrounding areas, and a thorough inspection of evidence, lockers, gym, office spaces,” Luna said.

“We have looked at everything out there that we possibly could.”

“We know one device exploded and we have not recovered any evidence from a second device on that scene,” said Kenny Cooper, special agent in charge of the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) L.A. Field Division.

They confirmed that there was no public access to the investigation site and they do not believe the grenades were lost in transport between Santa Monica and the training facility.

Following the deadly incident, Luna said he has called for an “independent review of the policy and practices as they relate to the LASD explosives detail.” ATF detectives are assuming full control of investigating the whereabouts of the second missing grenade, while LASD homicide detectives will investigate the deaths of deputies.

“Since this tragic incident, all future explosive devices, inert or not, will be treated as if they are all live and will be disposed of accordingly,” Luna said. “We need to know what happened. We owe it to the families.”

On July 21, LASD officials, along with agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), conducted a search at a second location in Marina del Rey as they work to track the grenades’ origins.

Details are limited, but footage from the scene showed authorities swarming the Villa Del Mar Apartments in the 13900 block of Marquesa Way. A robot was used to search several storage units in an alley behind the apartment complex and a boat at the marina was also searched.

Investigators have not released details on their findings and so far, no suspects have been named and no arrests have been made. The explosion was the single deadliest incident for the department in more than 150 years.

“These brave men served with honor, courage, and unwavering commitment to protecting and serving our community,” the sheriff’s department said. “Their tragic loss is deeply felt across our Department and the entire LASD.”

The fallen deputies served a combined 74 years with the department. Between the three of them, they leave behind 16 children, along with devastated friends and family members.

A final report on the investigation is expected to be released in the days ahead, Luna said.