The San Jose firefighters union is offering a $10,000 reward for information leading to the arrest of a man who authorities believe set eleven of thirteen fires in the city since last Wednesday.

The latest fire early today near Alum Rock Park stoked new fears that a serial arsonists is setting fires across San Jose in California's South Bay. And while today's fire was not a case of arson, according to Fire Capt. Cleo Doss, the fire department has confirmed that there were three more arson blazes set just on Sunday.

"We are working collaboratively with the Police Department and other agencies," Doss said. "This is an active and aggressive ongoing investigation."

"We are hoping people will be patient with us. This could take some time," Doss added.

The search for the suspect has intensified, with community members getting involved this weekend, picking up fliers from a local fire station to distribute throughout several downtown neighborhoods, hoping to get a lead. The fliers show a sketch of the suspect, created using surveillance videos from homes in the area, authorities said.

The suspect is described as a white or Hispanic man with medium-length dark hair. He is between 25 to 40 years old and 6 feet to 6 feet 2 inches tall, weighing between 160 and 180 pounds, authorities said.

City Councilmember Sam Liccardo told ABC News' Los Angeles station KABC that community members should consider taking extra precautions to avoid blazes around their homes.

"We want to make sure people clear out anything that's flammable from their front yards and we want to make sure everybody sees the sketch of the suspect, that they've got the 911 number and the hotline number for arson," Liccardo said.

Doss urged people who see "suspicious activity" to report it, "no matter how little it is."

"Do not confront them. Call 911," Doss said. "It's important to clean up front yards of debris and patio furniture on the porch which can be set on fire."