Towels soaked in linseed oil caught fire early Friday morning and caused the partial evacuation of a senior living apartment complex on the northwest side.

Crews were alerted to the fire at about 4 a.m. when sprinklers were automatically activated inside Amber Lights at 6231 N. Montebella Road, near the intersection of West Orange Grove Road and North La Cholla Boulevard.

While the first engine company was en route, an emergency dispatcher telephoned Amber Lights to confirm the fire, said Capt. Adam Goldberg, spokesman for the Northwest Fire District. Nursing staff told the dispatcher smoke was filling the first floor of the large, three-story complex.

The first company arrived within three minutes and found moderate smoke on the first floor of the building. Further investigations found a fire burning in the maintenance and laundry area, Goldberg said.

Six apartments closest to the fire were evacuated.

The activation of the sprinkler system had extinguished most of the fire and the first crew on scene extinguished the remaining flames within 10 minutes while other engine companies set up large fans in the building to blow out the smoke.

They also temporarily drained the sprinkler system to stop the flow of water into the building.

“The sprinkler system was secured, but not before leaving three inches of water throughout most of the first floor service areas,” Goldberg said.

“A Northwest Fire investigator has determined that the fire was accidental in nature, caused by a large pile of towels that had been used to clean and recoat doors with linseed oil the day before. Linseed oil is used as a varnish or coating to preserve wood. The towels were not dried before storage and a chemical reaction from the oil gave off enough heat to ignite the towels,” Goldberg said.

To prevent a chemical reaction that may result in a fire Goldberg said, ideally, rags used to apply linseed oil should be laid out to dry or line-dried in an open-air area, not bunched up.

Rags also can be placed in an airtight, fireproof container, such as a tin, which prevents oxygen from combining with fumes to create a chemical reaction and causing a fire.

Damage at Amber Lights was estimated to be about $5,000.