SAN FRANCISCO -- Power has been restored to all 8,600 customers who lost electricity after Friday's underground explosion and fire in San Francisco's Tenderloin neighborhood.

Andrew Souvall, a spokesman for PG&E, says the final few hundred customers still without power on Saturday had it restored just after 6 p.m.

Crews continued to work to determine what caused a manhole at Polk and O'Farrell streets to erupt in smoke and flame at around 11 a.m. Friday, knocking out power to over 8,000 area residents.

It was originally reported that a transformer had exploded, sparking the underground fire, but on Saturday PG & E said there was no explosion.

“There was no explosion. There was a fire,” said PGE Spokeswoman Nicole Liebelt, “There is no transformer in the vault. It [contains] electric cable service and switches.”

Firefighters responded to the scene, putting carbon dioxide on the blaze to deplete the oxygen in the hole and try to put out the fire, fire Lt. Mindy Talmadge said.

Once the fire appeared to be contained, Talmadge said PG&E officials asked firefighters to pull out the carbon dioxide to allow the equipment to be fully disabled. Another fire erupted shortly afterward.

Though power has since been restored to most who lost it Friday, twenty four hours later, residents were still in the dark. At a nearby senior apartment complex on Polk Street, some chose to stay inside, others had no choice.

The elevators weren't working so Lucky Davis was not able to go up to his 5th floor apartment. “It’s a disaster for me,” said Davis. “I had to sleep in the lobby all night.”

Davis was offered shelter at another facility, but he thought power would have been restored by morning. He waited for most of Saturday outside, while inside his food was spoiling.

The Red Cross was called in to bring food to the seniors. Residents in the surrounding neighborhood just tried to cope the best they could in their darkened apartments.

PG & E says it realizes the outage is a major inconvenience.

“We understand that our customers do want to know what took place yesterday and what the cause was,” said Liebelt. “We do as well, and we are committed to thoroughly investigating what took place here.”

As Sunday afternoon, O’Farrell remained closed between Larkin and Van Ness Street. Polk is closed between Geary and Ellis streets.