Rampaging wildfire burns 6,500 acres near Anchorage, Alaska

© Alaska State Troopers
The Sockeye Fire grew quickly late Sunday and early Monday.

Homes were being evacuated and fire crews from the lower 48 states were racing to a wildfire north of Anchorage, Alaska, that grew to 6,500 acres in just hours, authorities said early Monday.

The so-called Sockeye Fire, in the town of Willow, about 80 miles north of Anchorage, forced firefighters on the defensive as aircraft continually drop water and fire retardant Sunday night, the state Forestry Department said.

Residents began fleeing from a voluntary evacuation area covering both sides of a 15-mile stretch of the George Parks Highway. As of Sunday evening, more than 200 people had signed into one evacuation center near Talkeetna. But the total number of evacuations wasn't immediately available.

The fire was first reported at 1:15 p.m. (5:15 p.m. ET) as covering 2 acres and quickly grew. By 3 p.m. it had reached 80 acres, and by 6 p.m. it covered 1,077 acres along the western shore of Kashwitna Lake, the Forestry Division said. By 10:30 p.m., the fire had grown to 4,183 acres. Two hours later, it was estimated at 6,500 acres.

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The cause of the fire — which was quickly classified as a Type 1 incident, the most complex fire to deal with — remained unknown, the agency said. It was moving south late Sunday night, officials said.

There are 1,700 homes in the evacuation zone.

One firefighter was treated for heat exhaustion, according to an update from officials in Matanuska-Susitna Borough.

The entire Matanuska-Susitna Borough Fire Department was at the scene, along with crews and helicopters from Anchorage, Fairbanks, Kenai, White Mountain, Alaska Fire Services and the Forestry Division. At least 10 hotshot crews from other states were on their way, the Forestry Division said, along with three Alaska Air National Guard Blackhawk helicopters to help with bucket work on the fire.

"It's moving pretty fast, and we're throwing pretty much everything we have at it," Tim Mowry, a spokesman for the Forestry Division, told NBC station KTUU of Anchorage.

Patty Sullivan a spokeswoman for Matanuska-Susitna Borough, said the fire quickly jumped Sockeye Avenue and then the Parks Highway, which is also known as Interstate A-4.

Sullivan urged people to steer clear of Willow, noting that's it's a major center for dog mushing, and many dogs and their gear must be evacuated along with their owners.