One person was killed and two were injured in a gas leak explosion in Aliso Viejo Tuesday, authorities said.
U.S. officials confirmed it had responded to an explosion. "Investigation is in early stages, as information is confirmed we will share it".
The address corresponds to a medical office building with multiple practices inside, online records show.
Brian Fennessy, the Orange County Fireplace Authority chief, stated 70 firefighters had been dispatched in response to the decision in Aliso Viejo at 1:09 p.m. native time.
FBI spokesman Mike Gifford said the cause of the explosion is still unknown and the agency has sent resources to help with the investigation, which is being led by Orange County Sheriff's Department, local news outlet City News Service reported. There were early reports that a vehicle had crashed into the building, but that turned out not to be the case.
Those who were injured were transported to the hospital, according to the sheriff's department. Investigators are interviewing the three injured.
Authorities say one person is dead and two others have injuries after an explosion rocked a Southern California office building.
"This is going to be a slow process", Bommarito said.
At this point, officials are not ruling anything out.
The blast involved a building under renovation but the cause was not immediately known, Fennessy said.
Authorities had not found an explosive device Tuesday night but were searching through debris that was left after the blast.
Nothing indicates there were any threats made before the blast, which appeared to be concentrated in a suite on the first floor of the office building, Sawyer said.
The FBI said there was no initial indication of terrorism, but the agency would continue to investigate.
The Bureau of Alcohol, Tobacco, Firearms and Explosives responded to the incident.
He said it felt "almost like an quake, but a big natural disaster".
A woman who was on her way to an appointment in the area told CBS2 she arrived just after the blast occurred, and she saw fire on the roof of the building.