Neighbors say they were startled by a series of booms just before 5 p.m.
"I heard like a boom, and then smoke started rising up. We were at a barbecue," said neighbor Rob Datta.
"We heard three loud bangs," said Sunni Sahota who lives next to the house that initially caught fire. "It was after a few seconds... boom, boom, boom."
At first he says he thought it was the wind, but then he noticed the wood frame of the house next door was in flames.
"It was so intense so I started watering our house a little bit, trying to save it, but then I saw our fence, which we share with this house caught fire," said Sahota.
Other neighbors jumped on their roofs and began spraying them down to prevent the fire from spreading. Fire commanders say the afternoon winds did not help.
"Wind was blowing this way, bringing a lot of heavy embers and that type of thing, and it started a grass fire a couple fence fires and two residential structure fires," said Contra Costa County Fire Chief Ben Smith.
Two homes on Marvue Circle were significantly burned. Smith says the series of booms may have been from items inside a shed that caught fire in one of those homes.
"We did hear some propane tanks exploding," said Smith. "We had two gas lines involved on the secondary explosions at the start of the fire, that may have been what people were hearing."
PG&E says there was no damage to any of their gas lines, but meters were damaged, so they were called in to shut off gas while firefighters were working to control the flames.
No one was injured in this fire. The house where this all started had no residents.
One of the families of a home on Marvue will be able to return to their home Tuesday as the damage was not significant. Unfortunately the other home on Marvue has been yellow-tagged by the fire department.