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An explosion at a medical office building in Aliso Viejo on Tuesday left one woman dead and three others injured and prompted the evacuation of nearby buildings, including a preschool, officials said.

The incident happened around 1 p.m. in the first floor of a two-story office building, Capt. Tony Bommarito with the Orange County Fire Authority said. The building is located at 11 Mareblu, OCFA tweeted.

A building in Aliso Viejo is seen after a fatal explosion on May 15, 2018. (Credit: KTLA)
A building in Aliso Viejo is seen after a fatal explosion on May 15, 2018. (Credit: KTLA)

Bommarito called the damages “severe,” with walls and windows blown out and debris landing onto the street and in the parking lot next door.

But investigators were puzzled at to what the cause of the explosion was and had not recovered any type of device from the location as of Tuesday night, said Dave Sawyer, a commander with the Orange County Sheriff’s Department.

“We can not say exclusively that this explosion was intentional,” Sawyer said. “As soon as we can confirm that information, we will share it with you.”

However, one federal official told the Associated Press that it was believed to be an intentional act and may have been set off by a package.

Sawyer did note that the size of the explosion alone was enough to make it suspicious.

Employees told KTLA that firefighters who responded to the scene had described it as a domestic incident, but when asked about that at an evening news conference, Sawyer said he had not seen any evidence to indicate it was domestic in nature.

The woman who died in the incident was in close proximity to the blast, Sawyer said. Coroner’s officials were still working to positively identify her remains.

Authorities could not provide the status of the three individuals taken to the hospital but said they were being interviewed about the incident. They were likely in close proximity to the person who was killed in the explosion, Sawyer said.

Other business owners in the building told KTLA the explosion occurred in the office of an aesthetician practice called Magyar Kozmetika. A woman named Ildiko owns the practice, they said, but her business partner had been unable to contact her on Tuesday.

The FBI sent resources to the scene. Agency spokesperson Mike Gifford, however, said there was no early indication of terrorism, CNN reporter Kristen Holmes tweeted.

A still from surveillance cameras provided by Kennedy Chiropractic shows investigators as they probe an explosion at an Aliso Viejo building on May 15, 2018.
A still from surveillance cameras provided by Kennedy Chiropractic shows investigators as they probe an explosion at an Aliso Viejo building on May 15, 2018.

Officials from the Bureau of Alcohol, Tobacco, Firearms and Explosives and Department of Homeland Security were also involved.

“They are not assuming the investigation at this time,” Sawyer said. “They’re merely assisting us based on the nature of the incident.”

He added, “I think this whole thing is suspicious just by nature.” However, there were no suspects in the case and no arrests had been made.

The address where the explosion happened corresponds to a medical office building with multiple practices inside, online records show. The building is on a cul-de-sac; another large medical building for Memorial Care Medical Group is next door, and a private preschool, Academy on the Hills, is across the street.

Surrounding buildings also sustained damages, but nobody was injured outside the office where the explosion occurred, Sawyer said.

Images shared by Kennedy Chiropractic, which operates in the building, from its surveillance cameras showed the practice’s roof had partially caved in. But no one in that office was hurt because no one was scheduled to work until about an hour after the blast, employee Rose Marie Fernandez-Morris said.

But Hailey Everett, who works at a dental office on the first floor, was there Tuesday morning as the building suddenly shook.

“There was a really loud boom,” she told KTLA. “I thought that maybe there was an earthquake, but I turned around and the ceiling behind me in my office had caved in.”

Everett said she was thankful to have only required treatment at the scene for a bump she suffered on her head after being struck by a dislodged ceiling chunk.

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. (Credit: KTLA)
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. (Credit: KTLA)

Sky5 footage showed crews evacuating people — including children, some in cribs — out of the Academy on the Hills.

“There was a big noise and then I thought it was a garbage truck, but it was a big loud brick that fell off the building, it was a lot of them crushing down,” a 6-year-old named Kingston told KTLA.

Raul Hernandez, who also witnessed the incident, said he saw women running across the street with the faces bloodied, one of them with the hair in the back of her head completely singed.

Kingston’s father described the incident as “pretty freaky, to say the least,” but said he was sure the children at the school were safe.

“That’s all we could hope for,” he said.

Parents whose kids were evacuated could reunite with them at the parking lot of the Target store on La Paz Road, OCFA tweeted.

The fire had been put out but a bomb squad and a hazmat team remained at the scene to assess the area’s safety,  Bommarito said.

“This is going to be a slow process,” Bommarito said. “We have an explosion, which is not a common thing.”

Roads in the area had been shut down amid the investigation but later reopened once the building was deemed safe.

A deputy told KTLA earlier that a gas leak caused the explosion. OCFA initially said a vehicle crashing into a structure at 5 Mareblu led to the incident.

KTLA’s Jennifer Thang, Wes Woods II and Erika Martin contributed to this story.