May 15 (UPI) -- One person died and at least three more sustained injuries after an explosion at a medical building in California, authorities said Tuesday.
The Orange County Fire Authority said one person who was inside the building in Aliso Viejo died at the scene.
The explosion occurred at about 1 p.m. and caused damage to the first floor of the two-story building, which was under construction.
Officials declared a second-alarm fire and hazmat situation, and crews successfully extinguished a fire at the building after the explosion.
Officials originally believed the explosion was caused by a car crashing into the building, but Orange County Sheriff's Department spokeswoman Carrie Braun said no car was involved and the department was investigating how the explosion occurred.
Bomb squad investigators and the FBI worked to determine the cause of the blast, but authorities said there was no ongoing threat to the community.
Officials didn't consider the explosion suspicious and they found no explosive devices. The FBI also said there was no indication of terrorism, but it would continue to investigate out of caution.
Law enforcement ordered nearby Academy on the Hills day care and preschool to evacuate and children were rolled in cribs and walked hand-in-hand down the street.
Authorities also ordered a full closure of eastbound Pacific Park.