USA officials confirmed it had responded to an explosion.
An explosion at a California medical building that killed one person and injured three others is being investigated as intentional, the Associated Press reports.
Authorities initially indicated a auto had crashed into the building, but Bommarito said later that did not appear to be the case.
Chief Fennesy noted the building where the explosion occurred was being renovated.
However, Orange County Sheriff's Department spokeswoman Carrie Braun said no auto was involved in the explosion and there is an investigation to find out what caused it, according to NBC.
Late Tuesday afternoon, NBC4 - citing unnamed federal sources - said investigators had determined that the blast was an "intentional detonation", and the explosive device was delivered to the building, addressed to a specific person. The condition of the injured were not immediately known.
The county's bomb squad and a hazmat team are preparing to search the building where the explosion occurred.
"As far as what I'm hearing there was no vehicle involved", Carrie Braun of the Orange County Sheriff's Department said. Firefighters arrived and extinguished a fire, OCFA Capt.
McWilliams said she saw two burned women staggering out of the building, covered in ash and soot.
Children are seen being wheeled out in cribs as crews evacuate the preschool Academy on the Hills after a fatal gas leak explosion at a nearby office building.
The fire at the building at 11 Mareblu was quickly doused following the roughly 1:10 p.m. explosion. OCFA said a bomb squad was sent in to assess the situation and investigate the cause of the blast. No children were injured, officials said.