A spate of trash fires set in the Santa Rosa area over the weekend might be connected to two similar sprees in recent months, fire officials said Monday.

Eleven fires were set in dumpsters and trash cans between Friday and Sunday evenings, mostly in northwest Santa Rosa. No serious damage or injury was reported.

Many of the fires were set in commercial garbage bins. Two were in residential trash cans set out in carports, Santa Rosa fire inspector Toby Rey said.

The pattern is similar to two series of fires in January and October.

In October, several fires were set in trash cans on Santa Rosa Avenue south of Highway 12, Rey said. In late January, four trash fires were lit in one day, all in the northwest Santa Rosa area, Rey said.

A man riding a bicycle was seen in video footage or described by witnesses in each of the three cases. The fire department hasn't identified a suspect, but is working on a general physical description based on witnesses' accounts.

"I'm working on the principle that this is one guy," Rey said.

In most cases, the fires were set with easily combustible trash, like cardboard boxes, that had been set out by the business or homeowner, said Acting Fire Marshal Mark Pedroia. People can help prevent such fires by waiting to set out their trash until close to the time of garbage pickup, he said.

The Santa Rosa police and fire departments are continuing to investigate the case. Anyone with information can call the Fire Department at 543-3500.