Three members of the Los Angeles County Sheriff’s Department’s Arson/Explosives Detail were killed Friday morning in an accidental explosion at the Biscailuz Training Facility in East L.A.

The blast occurred around 7:30 a.m., reportedly involving an explosive device believed to be inert after a routine callout.

The victims, described as highly experienced, had a combined 74 years of service.

No one else was injured. The incident marks the department’s deadliest day since 1857.

An investigation is underway with support from the LAPD, FBI, and ATF, ABC 7 News has reported.

A procession and tributes are being held in their honor.

Written by B.C. Begley