CALGARY - Investigators are still working to determine the cause of Tuesday’s industrial fire, but Alberta Occupational Health and Safety is speculating on the origin. Officials with OHS suggest a demolition crew working at the site may have inadvertently started the fire at IKO Industries Tuesday morning. Fire crews remained on scene overnight and into Wednesday to douse hot spots. “In the middle of the night the winds picked up a little,” says Carol Henke of the Calgary Fire Department. “So we did have a flare-up, but crews got it under control." Henke says an investigation into the cause won’t begin until all the hot spots are put out and the site is safe enter. IKO manufactures shingles and other roofing materials, and has had several fires in the past. “Once the investigation is completed then that will determine the course with future investigation with the Alberta fire code,” says Henke. “But we don't want to speculate with that.” OHS confirms 13 fires at IKO were reported between February of 2002 and December of 2009. All of those fires were related to the storage and processing of materials. Since the last fire was reported in December of 2009 -- OHS says the company has shown some improvement in its fire management practices.