He said investigators had not found an explosive device at the scene.
Officials originally believed the explosion was caused by a auto crashing into the building, but Orange County Sheriff's Department spokeswoman Carrie Braun said no vehicle was involved and the department was investigating how the explosion occurred. The person who died was inside the building at the time of the blast, officials said.
The FBI is responding to the scene, a law enforcement official told CBS News senior investigative producer Pat Milton.
Orange County Sheriff's Cmdr. McWilliams says one woman had skin peeling on her arm.
The blast involved a building under renovation but the cause was not immediately known, Fennessy said. There were early reports that a auto had crashed into the building, but that turned out not to be the case. The cause of the blast is being investigated. The injured were taken to a hospital. No children were hurt, officials said. They were being reunited with parents at a nearby store parking lot.
"The survivors' injuries were consistent with an explosion, but not necessarily consistent with a bomb". Officials said the structure, which fire officials described as a medical office building, appeared to be under construction.
Although the cause of the blast was still unknown, Bommarito told reporters around 3:30 p.m. that there was "no immediate hazard" to the community.
Treasury yields surge pushes Wall Street lower
The Dow Jones industrial average fell 193 points to close at 24,706.41, with Home Depot among the biggest contributors of losses. Stocks struggled to a mixed finish on Wall Street as weakness in smaller-company stocks offset gains in large companies.
White House calls deaths in Gaza 'propaganda' by Hamas
The Palestinian Health Ministry said more than 1,600 had suffered injuries, and that numerous dead had not yet been identified. Israel said some 40,000 Palestinians had taken part in " violent riots " at 13 locations along the Gaza Strip security fence.
Japan GDP Slides In 1st Quarter Ending 8 Quarters Of Growth
External demand - or exports minus imports - added 0.1 percentage point to first-quarter GDP, as imports slowed more than exports. Economists say Japan's first-quarter contraction is temporary, but the rebound will not be almost as strong as previous quarters.
'Cure' for common cold could 'block virus in minutes'
By contrast, the new molecule successfully blocked the several strains it was trialed against without damaging the human cells. According to scientists, the common cold could be cured within five years - by using an inhaler at the first sign of sniffles.
Kia Motors Will Debut 48V Diesel Hybrid Powertrain This Year
Kia has announced plans to introduce new mild hybrid technology to its line-up, similar to the drivetrains now utilised by Audi. The battery recovers energy from the diesel engine's crankshaft when the vehicle is decelerating or driving downhill.