Crews were battling a large fire that erupted Sunday afternoon at Burns Bog, a beloved nature conservation area in Delta, B.C., just south of Vancouver. The fire began just before noon and quickly grew, fanned by strong winds. But late afternoon, about 80 firefighters were called to fight the blaze, along with five air tankers and four helicopters. Thick smoke could be seen billowing in the air and shrouding an adjacent highway. The Delta Police Department said in a release Sunday afternoon that the fire had forced the evacuation of a nearby industrial area, but there was no immediate risk to residential areas. There were conflicting reports about the size of the fire. Earlier in the day, Delta Mayor Lois Jackson put the fire's size at 100 hectares. Later, a spokesperson for the BC Wildfire Service said it was 50 hectares. At a news conference Sunday afternoon, a Delta fire official said the fire had grown to an unknown size. Jackson said she did not know what caused the blaze. "My experience has been there's very few fires that have started in the bog that have been natural causes. Usually it's people, but time will tell," she said. The fire was situated between 72nd and 80 Streets. Police closed Highway 17 from Highway 99 to the Nordel Connector, and traffic is being diverted. Burns Bog is a raised peat bog, which covers approximately 3,000 hectares of the Fraser River delta, between the south arm of the river and Boundary Bay, according to the Delta district website. It's approximately eight times the size of Vancouver's Stanley Park. Fighting a fire on a bog can be challenging, Jackson said. "In some of these areas . . . you just a have layer of peat and below that you have a lot of deep water." Burns Bog is the largest undeveloped urban land mass in North America, and home to 175 bird species, 41 mammals as well as rare plant and berry species, according to its website. Nearly seven years ago, another fire at the bog burned for nearly two weeks.