A U.S. official told the Associated Press the authorities were investigating it as an intentional act and a package may have caused the blast. No children were hurt, officials said.
Officials didn't consider the explosion suspicious and they found no explosive devices. However, authorities will continue to investigate possible terrorism out of caution.
Police investigators and FBI agents are studying the causes of the explosion, and they assure that there is no lingering threat to the community.
Associated Press writer Michael Balsamo in Los Angeles contributed to this report.
"We have confirmed there was no vehicle inside", Bommarito said, adding there was an explosion inside the building.
Mary McWilliams of San Clemente tells the Orange County Register that she saw two women with burns stagger out of the building.
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The drama thriller has become one of the most loved and talked about shows in recent times, all thanks to its gripping storyline. According to the magazine, Priyanka's show has been averaging 2.4 million viewers and a 0.5 in the 18-49 demographic.
Dong Shin said he had seen "fire, smoke, insulation popping out of the walls, a lot of scared people running around, a lot of commotion".
Orange County Sheriff's Cmdr.
In an evening briefing, Orange County and federal officials said no cause had been definitively determined or ruled out, whether a gas leak or an intentional act.
Mary McWilliams told the Orange County Register she arrived for an appointment to find smoke surrounding the area and auto alarms going off.
McWilliams says she saw two women covered in ash and soot stagger out of the building.
"Take care of my mother, take care of my mother!" shouted one woman as she fled, according to NBC4. The other woman was bleeding from her head.
Afghanistan: 9 killed in Jalalabad attack
On May 6, an explosion at a mosque in the eastern Afghan province of Khost killed at least 10 people and wounded 29. The attack targeted the tax and revenue office of Nangarhar Province in the city center of Jalalabad on May 13.
Authorities say they're trying to figure out whether the explosion was accidental or intentional.
Officials haven't released information about the person who was killed.
The dead and injured have not been named.
They said they were not actively looking for any suspects. The blast involved a building under renovation but the cause was not immediately known, according to authorities. OCFA said a bomb squad was sent in to assess the situation and investigate the cause of the blast. The injured were taken to a hospital.
Little children holding hands and others being pushed in rolling cribs were led by firefighters to a Target parking lot to be united with parents.
Of the three people who were injured, Ms. Braun said, two suffered "significant" injuries while the third complained of smoke inhalation.
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