Surveillance cameras captured the images of three young men behind a Santa Rosa Avenue motorcycle gear shop when a fire broke out, damaging the business, a Santa Rosa fire official said Wednesday.

The video strengthened investigators' determination that the fire outside The Cycle Gear shop on Saturday morning was arson. The tapes have been given to Santa Rosa police, said Scott Moon, Santa Rosa Fire's senior inspector.

The fire started in a dumpster against a metal door to the building. Heat permeated the metal and ignited stock inside, Moon said.

A sprinkler system doused the fire. Damage was estimated at about $40,000 to the structure and its contents.

A spree of small fires set in dumpsters and other areas around town in the last year appear to be unrelated to Saturday's fire, Moon said. Fire officials have suspected those were set by a person on a bicycle.