Firefighters say a burning candle in a nearby tent caused the fire. They also say gusting winds spread the fire quickly.
From Sky 7 you could see thick dark plumes of smoke.
"This was all black," said Rodney Stanley of G&S Paving Incorporated.
Rodney Stanley got the call just after 530pm for a vegetation fire that had spread to a nearby junk yard. His family's paving equipment was parked there.
"When you work for that and to see it could be gone it's scary because that's what puts food on the table," said Jason Stanley of Sunrise
Grading and Paving.
Officials issued a public health advisory due to the smoke.
"The stuff that's burning is particularly nasty it's tires and upholstery and seats," said Robert Marshall, Fire Marshal for Contra
Costa County Fire Protection District.
Helicopters dropped water from overhead.
"It looks like it's getting under control and just pray that there's minimal damage," said Jason Stanley.
Investigators quickly determined the cause.
"A candle in a tent as part of a homeless encampment," said Marshall.
Officials say on firefighter injured his hand but returned to fighting the fire. Two more people suffered minor burns and smoke inhalation.
One of them was taken to the hospital.