Whitehorse's fire chief said a blaze that destroyed a family's home Thursday was likely caused by a compact fluorescent light bulb with a fake safety certification mark.

The owners of the house, located on Fir Street in the city's Porter Creek subdivision, arrived at home that afternoon to find it uninhabitable because of the blaze.

"It's believed that a faulty compact fluorescent light bulb was the cause of the fire. Everything's pointing to that to be the cause," Whitehorse fire Chief Warren Zakus told CBC News on Friday.

"We had received some information that there were some compact fluorescent light bulbs that were causing some fires. We checked all the bulbs in the house, and we did find some bulbs in the house that did match some of the ones that [the Underwriters' Laboratories of Canada] has put an alert out for."

An alert on the independent product-safety-testing organization's website shows one questionable light bulb, a Globe Mini-Spiral 13-watt bulb, has a fake certification mark on it and "may pose a potential fire and electric shock hazard."

The alert, posted in 2004, stated that the bogus light bulbs were manufactured in 2002 and 2003 by Fujian Joinluck Electronic Enterprise Co. Ltd. in China. The ULC recommends consumers with those bulbs return them to retailers immediately.

A police officer called in Thursday's fire just after 3 p.m. PT, after seeing smoke from the house. Four fire trucks and more than a dozen firefighters responded and spent nearly four hours fighting the flames.

While they saved the two-storey structure, the house sustained fire and water damage to both floors. Zakus said nearly everything is damaged, and estimated the total loss at around $250,000.

Whitehorse RCMP are investigating the blaze.

Police are also investigating another fire in the same area Thursday night. Firefighters spent nearly three hours putting out a fire at a Maple Street home, which had three rooms damaged.

Zakus said that fire appeared to have been deliberately set. As was the case in the afternoon fire, no one was in the house when firefighters arrived.