Calif. explosion seemed like 'end of the world'

>>> good evening. we come to you tonight from a huge hollywood sound stage where later this evening we'll be hosting " stand up to cancer ." we'll have more on that a bit later on in this broadcast.

>>> we must begin with a major news story just up the coast from us here in california. it was dinner time last night, about 6:15 in san bruno , california, the routine of a normal thursday in the neighborhood was shattered by an explosion so loud it was heard for miles. then came the geyser of flames shooting 300 feet in the air and then the noise. people near the blast zone understandably thought it was an earthquake, a nuclear explosion , perhaps a plane had gone down. turned out to be a natural gas line exploding and a fire that wasn't brought under control until just this afternoon. san bruno is a city of about 30,000 people, give or take, just south of san francisco , just west of that city's airport, sfo. federal investigators have converged on the neighborhood where the gas main blew up. we begin our broadcast tonight from the scene. our own kristen welker and miguel almaguer are there for us. good evening.

>> reporter: good evening, brian. the blast has already been called a state of emergency . this city reeling from an explosion so powerful it claimed lives and forever charred the landscape here. as day broke in a neighborhood not far from san francisco international airport , smoldering debris from 38 burned-out homes is all those left. firefighters hosed down hot spots as dogs searched the rubble. four are confirmed dead , a number authorities fear could rise. a massive water-filled crater marked the center of the blast.

>> we thought a jet had gone down.

>> reporter: at dinner time thursday, a gas-fuelled fireball shot hundreds of feet into the air. the explosion forcing families to run for their lives.

>> i seen a chunk of concrete fly out the size of a car.

>> reporter: windows shattered, asphalt melted. the force of the blast was felt miles away . it was chaos and confusion. one residence department catl one residence department c called it hel l on earth. i thought it was an earthquake.

>> i looked out the window and saw this huge explosion.

>> reporter: an ttoiantoinette was doing paperwork. didn't think you'd make it out?

>> i didn't.

>> reporter: the fire spread instantly from house to house. firefighters struggled to control the growing blaze, hampered by exploding gas lines and fire hydrants with no water source .

>> it was difficult to approach. we couldn't be successful putting out the fire with the supply being shut down.

>> reporter: the cause of the blast is under investigation, but the local gas company, pacific gas & electric , says a 30-inch gas line likely ruptured. a google earth image from 2007 shows the spot had been marked for maintenance or repair. today, that spot was still too dangerous to reach. now the search for answers begins in a community torn apart by a blast where little is left standing. miguel almaguer,