A rampaging wildfire in northern B.C. has closed the Alaska Highway between Watson Lake and Fort Nelson, and has forced the evacuation of three highway communities.

The Smith River fire, burning 18 kilometres from the Liard Hot Springs, ran 20 kilometres overnight, and grew from 2,000 hectares to 10,000 hectares, fire information officer Jill Chimko of the Prince George fire centre said today.

Chimko said the evacuation order for the communities of Fireside, Coal River, and the nearby Muddy River Indian Reserve was issued shortly after noon.

Approximately 109 residents are being relocated to the Watson Lake Recreational Centre, she said.

Chimko said the Smith River fire is travelling in a northwest direction, about 14 kilometres from Fireside and Coal River.

Should it turn westerly, however, the communities could be threatened, she said.

"The wind is predicted to switch and move in from the east," she said. "If that does occur, there is the potential a fire will approach the highway again."

Chimko said the blaze is staffed by 90 firefighters and 10 supervisory personnel.

"At this point, we have not called for any additional firefighters but we have definitely done an inventory of what is available to use provincially."

Air support for the Smith River fire effort is making use of the Yukon's air tanker base in Watson Lake.

Meanwhile, with no immediate end of extreme forest fire conditions in sight, Wildland Fire Management is taking stock of available firefighting resources outside the territory.

Mike Sparks, wildfire operations manager, said eight more firefighters were arriving from Alberta this morning to assist the 21 Yukon crew members working the 80-hectare Mayo 2 burning 50 kilometres west of Mayo.

It's expected the gradual breakdown of the high-pressure ridge over the Yukon in the next couple of days will bring additional lightning activity with very little rain, he said.

Also arriving today were three more superisory personnel from Alberta and one more from B.C.

Sparks said the Yukon is looking to beef up the roster of available duty officers in the district offices in anticipation of worsening fire conditions.

A crew of 21 firefighters and one supervisor arrived earlier this week from B.C.

Volunteer community fire departments are also stepping into the mix by assisting with regular patrols of popular remote public camping locations between 1 p.m. and 9 p.m. each day, he said.

Wildland Fire Management, Sparks noted, is also aware that its high school graduation season, and a time for bush parties.

The volunteer departments are equipped with the necessary four-by-four suppression trucks, and bring a valuable asset in their ability to patrol the public areas, just as they did during the 2004 extreme fire season, he said.

Sparks said all burning permits have been cancelled, and staff are keeping an eye on what the weather will bring over the next couple of days as they contemplate whether to implement a ban on campfires.

Sparks said while temperatures are expected to drop through the weekend, they'll still be above seasonal norms, in the 19- to 20-degree C range.

It's also expected a new high pressure ridge will begin building early into next week, he said.

Currently, seven of the 10 districts, including Whitehorse, are under extreme fire danger ratings, two are high and only Old Crow is moderate.

In addition to the Mayo 2 fire, there is a 15,400-hectare blaze burning in the Dawson City district, though it is located in the wilderness zone and no action is being taken.