UPDATE 1:22 p.m.: Firefighters quickly controlled a structure fire that started Thursday evening at a four-unit residential complex at 11295 Los Osos Valley Road in San Luis Obispo, fire officials said today.

The complex was undergoing termite fumigation at the time of the fire, and started at the edge of the roof when an automatic floodlight turned on underneath the tent, according to a San Luis Obispo City Fire Department news release.

Bystanders tried to control the blaze using garden hoses, but they were asked to leave the area because of concerns over a possible release of hazardous chemicals associated with the fumigation.

Representatives from the fumigation company, which was not identified in a news release, arrived and told fire officials that the chemicals had been dissipating for several hours before the fire. Tests later showed very little residual gas remaining.

The structure fire caused about $10,000 worth of damage and was confined to a four-by-four section of the siding under a roof eave. No injuries were reported.

ORIGINAL STORY

This report as been changed to eliminate a specific brand of gas being used at the structure.

Fire crews have responded to a structure fire on 11295 Los Osos Valley Road, according to the San Luis Obispo Fire Department.

The structure is a two-story apartment complex that has been tented for what appears to be fumigation, according to the department.

Fire crews are taking it slow and treating it as a hazardous material incident because of a placard on the building warning of two gases used: sulfuryl flouride, a pesticide used to fumigate houses, and chloropicrin, a gas used as a "warning agent," fire officials said.

There was no one in the structure.

As of 8:49 p.m. crews were still dousing flames from the fire.