The blast at the two-storey building in Aliso Viejo, south of Los Angeles, also injured two people.
One woman was killed and three other people were injured in Tuesday afternoon's explosion in Aliso Viejo.
Orange County Undersheriff Don Barnes says the formal identification of the body was continuing but authorities believe it is that of Ildiko Krajnyak (IL-di-koh KRY-nyak), a licensed cosmetologist.
The fire at the building at 11 Mareblu - an outpatient medical clinic - was quickly doused following the roughly 1:10 p.m. explosion, but hazardous materials officials and bomb squad investigators were at the scene trying to assess the situation and ensure there was no further danger, Orange County Fire Authority Capt.
The explosion blew siding off the walls, exposing insulation and framing and shattering windows at the two-story building.
The Orange County Sheriff's Department stated in response to news reports: "Despite media reports quoting unnamed sources, we have not confirmed that the explosion is intentional, nor have we conclusively identified the source of the explosion". Police investigators and FBI agents are studying the causes of the explosion, and they assure that there is no lingering threat to the community.
A sheriff's official said late Tuesday that no specific device had been found.
As a result of the explosion one person is dead and three others obtained injuries of the different severity. Investigators were interviewing the victims Tuesday night.
"And the ground shook", he told CNN.
Families behind Indonesia bombings belonged to same religious study group
According to CNN , Indonesia has seen an increase in terrorist attacks beginning in 2014, mirroring an earlier trend in 2001. At Surabaya Centre Pentecostal Church, Futrianto then drove his vehicle onto the church grounds and detonated explosives.
"We are going to take every precaution necessary before we enter that building", Bommarito said.
At this point, officials are not ruling out anything.
Shin said it felt like "a big natural disaster", and as he and others rushed downstairs to get out of the nearby building, he saw two holes in the wall of the medical facility.
Officials said the blast appeared to be an intentional act caused by a package that specifically targeted the office where the explosion occurred.
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.
McWilliams said she saw two women walking out of the building, suffering from burns and covered in ash and soot. And there is no specific person that authorities are searching for right now, he added. A third victim was treated for smoke inhalation.
The sheriff's department is partnering with the FBI, the Department of Homeland Security and the Bureau of Alcohol, Tobacco, Firearms and Explosives, who will assist investigators.
Neighbors of Krajnyak said that she and her husband were separated but still living in the same house.