Multiple agencies, including the FBI, are investigating after an explosion underneath a tractor in Westmoreland County.

The explosion that killed three deputies at the Biscailuz Training Facility in East Los Angeles has reignited concerns over safety at Los Angeles County Sheriff's Department training sites.

Officials said multiple people were found dead after an explosion at the Horizon Biofuels plant in Fremont.

At least three deputies have died Friday morning after an explosion at a Los Angeles County Sheriff's Department training facility, officials said.

The explosion occurred midday Tuesday at Horizon BioFuels, a manufacturer of fuel pellets and animal bedding located in Fremont.

The Tuesday explosion of a wood pellet manufacturing plant in Fremont that killed a worker and two young girls was caused by a dust fire, an official said Thursday.

The explosion triggered a collapse, which made it dangerous for first responders to enter the building. Video obtained by sister station KETV shows the moment of the explosion at the plant.

Explosion at Fremont industrial plant The explosion at a Fremont industrial plant in a video obtained by the Omaha World-Herald.

At least three deputies were killed after an explosion was reported early Friday at an LA County Sheriff's Department training facility in East Los Angeles.

Three people have been killed in an explosion at a police training facility in Los Angeles.