SAN FRANCISCO — A fire that barreled through an apartment building construction site sending up black smoke that could be seen for miles around the San Francisco Bay smoldered into Wednesday morning as authorities worked determine what sparked the destructive blaze.
The exact cause of the fire — one of the city's largest in recent years — was under investigation, but crews were welding at the site of the blaze, San Francisco Mayor Ed Lee said. The five-alarm fire appears to have started above ground, according to Lee.
Crews prevented flames from spreading to nearby buildings.
The fast-moving blaze, which sent an enormous plume of black smoke into the sky, began around 5 p.m. Tuesday in San Francisco's Mission Bay neighborhood, a onetime industrial area that lies along the San Francisco Bay and is home to a University of California, San Francisco campus. Crews remained at the scene on Wednesday morning putting out hotspots.
Nearby buildings were evacuated as more than 150 firefighters battled the flames, using about 90 fire trucks, the San Francisco Chronicle (http://bit.ly/1cSlq6y) reported. Some front windows of Strata at Mission Bay, a building across the street, blew out from the heat of the fire. Residents of Strata remained evacuated on Wednesday morning.
San Francisco Fire Deputy Chief of Operations Mark Gonzales said exterior sprinklers on the building that went off have to be replaced and the fire protection system restored before residents will be allowed back in.
The fire also affected a nearby UCSF research building, where an ember was quickly put out after flying onto the roof, officials said.
"I think we're very lucky that the fire didn't jump anymore," Lee said.
The burning building was part of a residential development project with 172 units, according to BRE Properties, the building's owner. Fire-suppression systems had not yet been installed in the building, making the battle more difficult, fire officials said.
One of the six-story structure's walls collapsed about an hour after the fire began, and the rest of the building was not expected to remain standing, officials said.
Most of the construction workers at the site finished work for the day around 4 p.m., but several were still at the site when firefighters arrived, fire officials said.
One firefighter suffered first and second-degree burns to the face and hands, but was treated and released. Another had a minor ankle injury.
The site is several blocks from AT&T Park, the stadium where the San Francisco Giants play.