Gas explosion engulfs homes in San Francisco suburb

A natural gas pipeline explosion ripped through a neighborhood in a San Francisco suburb on Thursday, starting fires that burned more than 50 buildings and killing at least one person, officials said.

As many as 25 people were injured by the blast and flames in San Bruno, a few miles (kilometres) from the San Francisco International Airport, and have been taken to local hospitals and hospitals with burn treatment centres. The local coroner's office reported one fatality.

"We have confirmed that there are 53 structures, those are mostly homes, that were lost, about 120 damaged," Kelly Huston, an assistant secretary with the California Emergency Management Agency, told KTLA TV.

The gas line belongs to the northern California utility Pacific Gas & Electric Co, the company said in a statement.

"Though a cause has yet to be determined, we know that a PG&E gas transmission line was ruptured. If it is ultimately determined that we were responsible for the cause of the incident, we will take accountability," the statement said.

Water-dropping aircraft assisted fire crew in fighting the blaze, which was spread quickly by high winds after the explosion around 6pm (0100 GMT on Friday) local time.

"The fire is being contained at this point ... it is around 50% contained," San Bruno Fire Department chief Dennis Haag told a news conference.

Television footage showed a massive fireball and flames shooting skywards. Area residents said they first thought the blast's loud boom was the result of an earthquake or an airplane crash.