Authorities investigating the deadly explosion at a California day spa found a "destructive device" at a Long Beach residence and made an arrest, but the 59-year-old suspect is not being charged in connection with the blast, the FBI said Thursday.
Stephen Beal was arrested on suspicion of possessing an unregistered destructive device and is expected to make an initial appearance Thursday afternoon at the US District Court for the Southern District of California in Santa Ana, the bureau said in a statement.
The FBI said it would not provide further details until Beal was officially charged in court.
Police said Wednesday that the blast -- which killed spa owner Ildiko Krajnyak of Trabuco Canyon and injured three others -- was not an accident.
Two women, believed to be patrons of the day spa, are undergoing surgery and are expected to survive. A third woman suffered smoke inhalation and was treated and released at the scene.
The explosion Tuesday blew out walls and windows of the facility, heavily damaging the business, which was on the first floor of a two-story medical office building in Aliso Viejo, about 50 miles southeast of Los Angeles, according to Orange County officials.
Evidence indicated the materials believed to be involved in the explosion were not consistent with items used at a day spa, Orange County Undersheriff Don Barnes said Wednesday.
"At this point, our working theory is that this explosion was caused by a device," said Paul Delacourt, assistant director in charge of the FBI's Los Angeles field office.
Police have not commented on a motive, and Barnes said Wednesday investigators hadn't nailed one down, but an FBI spokesman ruled out terrorism. Nothing indicates any threats were made before the blast, Orange County Sheriff's Cmdr. Dave Sawyer said earlier.
Authorities served three search warrants Wednesday -- one at the Aliso Viejo business, one in Long Beach and one in Trabuco Canyon, Barnes said.
A voicemail message for the spa, Magyar Kozmetika, said Tuesday would be Krajnyak's first day back from a trip.
Dong Shin, a witness, said he heard a loud boom minutes before his Tuesday appointment in a nearby building.
"And the ground shook," he said. "While the ground was shaking ... my body jolted and my head hit the wall."
He also saw "fire, smoke, insulation popping out of the walls, a lot of scared people running around, a lot of commotion," he said.
The blast, which erupted around 1 p.m (4 p.m. ET), caused extensive damage to buildings in the area, Orange County Sheriff's Department Commander Dave Sawyer said.
In addition to the FBI, the Department of Homeland Security and the Bureau of Alcohol, Tobacco, Firearms and Explosives are assisting investigators.
- Arrest made in California blast probe, but suspect hasn't been connected to explosion, feds say
- Arrest made in connection to suspicious packages
- Multiple arrests made in connection with heroin trafficking organization
- Three arrests made in connection to burglaries targeting vacant homes
- Two arrests made in connection to burglarized homes; third suspect sought
- Feds probe USC over handling of sex harassment allegations
- Five suspects arrested in connection to Limestone Co. theft ring
- Feds allow Nestle to keep piping water in California forest
- Arrest made in connection to concession stand burglaries at Clements HS
- Explosion at FedEx near San Antonio could be linked to Austin blasts, FBI says