Fire damaging a Rohnert Park home started from a combination of fiberglass resin containers and paint cans tossed into a garbage can, Rohnert Park fire officials said Tuesday.

The Sunday garbage fire spread to an area between two homes on Bernice Avenue, causing as much as $40,000 damage, said John Marty, Rohnert Park's fire commander.

Callers dialed 911 starting at 3:46 p.m. Sunday, saying they'd heard the sound of minor explosions. Marty said that was from empty spray paint cans reacting to the heat.

Rohnert Park's two engines responded, along with an engine from Rancho Adobe and Rincon Valley fire agencies. A Rancho Adobe fire engine from downtown Cotati was enroute at 3:49 p.m. and arrived about one minute later, according to Rohnert Park dispatch records.

A Rohnert Park engine arrived just behind it, at 3:51 p.m., heading from the city's northern section, records showed.

Concerned the fire could spread further into the two homes, a Rohnert Park police sergeant overseeing the fire fight initially called for a second alarm, getting equipment started from agencies including Santa Rosa, Bennett Valley and Gold Ridge, according to Sonoma County emergency fire dispatch records.

That extra help was canceled after three minutes as Rancho Adobe and Rohnert Park firefighters quickly knocked down the flames. Marty said a lawnmower stowed next to the garbage can also caught fire - it's gasoline adding to the problem.

The homeowner had been working on a boat and had discarded the containers, not knowing they could spontaneously combust, Marty said. Rohnert Park fire officials issued a warning of the dangers of improperly handling such containers.