The fire grew to a raging inferno in minutes, engulfing nearly 50 cars.
The owner says it began when a worker was using a front loader to move cars around. He said possibly a spark from a battery hit a fuel line.
The smoke could be seen for miles in Contra Costa County.
Fortunately, the plume went straight up, but residents of a nearby senior center didn't take any chances.
"I told them to say inside because we were training to do that when something happens like this. To stay inside, then we don't breathe the poison," said Rodeo resident George Ortiz.
"I don't know, he said something about a car or something blow up. I don't know. And I guess it made a big flame," said another witness.
Fire crews from Rodeo, Hercules, Pinole and Richmond put out the fire. No one was hurt.
