A Vallejo fire battalion chief said when they arrived they swept through the building to make sure there was no one inside and then the stepped back and let it burn because the building was slated for demolition anyway. They just wanted to make sure it didn't spread.
Seven hours after the beginning of the fire, what's left of the building continues to smolder. Fire investigators have not yet determined the cause in part because it is still too hot to walk in to find the point of origin.
From a distance, a thick black plume of smoke pushed up into a clear Bay Area sky. John Lemoine saw the smoke from his home in Napa.
"I was on my way to shoot photos down in Berkeley and I saw the smoke and at first I thought it was the Napa Airport and I just kept driving towards it," said Lemoine.
He was not the only one drawn to the spectacle of the fierce fire. Quite a few people watched and snapped pictures of what used to be an enormous building getting gobbled up by flames. Lemoine says he often came here to snap pictures of the interior of this other derelict buildings here.
"There's a lot of history here, there's a lot of cool stuff, so it would be nice to see them use it for something, other than it just falling apart like this," said Lemoine.
Crews sprayed plenty of water on this fire, but they did not try to save the structure.
"This building and this whole north side of the island, you'll notice a lot of vacant buildings. We're going to be demoing, the city is going to be demoing these buildings out," said Vallejo Fire Chief Paige Meyer.
This is an area where local residents say homeless often hang out and when firefighters first arrived, they swept through the burning building to make sure no one was inside. Donnie Deck and two friends live in an abandoned warehouse just yards away.
When asked if he happened to have any friends or anybody who was in the building, Deck said, "Not that I know of... not that I know of."
Firefighters say they expect they expect the building to smolder for hours, so they posted crews out there to keep an eye on it and make sure that it doesn't flare up again.
As for concerns about air quality, ABC7 spoke with the Bay Area Air Quality Management District, who did receive a call from a person concerned about all the black smoke that was being pushed into the sky. They said they were thankful for some of the light breezes in the air and that those breezes helped dissipate the smoke pretty quickly.