The thick black smoke that could be seen from as far away as Mount Tam was coming from central Vallejo.
The fire was burning at a single-story commercial building on California Street off Sonoma Boulevard, just north of Valle Vista Avenue.
Firefighters say they now have it under control.
The call came in at about 4:45 p.m. Sunday. The fire quickly grew to two, then three, and finally four-alarms. We've been told it started as a grass fire then quickly spread to a tow yard west of the railroad tracks.
The entire street was blocked off.
The tow yard is in the middle of a busy commercial district. Vallejo Plaza is across the way and there's a lot of vehicle traffic on Sonoma Blvd. So the fire quickly caught the attention of Vallejo residents.
Some tweeted that the smoke was tough on their lungs. But the smoke did go down significantly about an hour later.
Though the fire is now under control, crews will remain on scene o mop up and keep an eye on hotspots.