Fire investigators believe an escaped debris burn started a late-season wildfire along the Glenn Highway south of Sutton, the Division of Forestry reported Sunday, as additional fires flared elsewhere in the Valley and strong winds kept firefighters on alert.

The 300-acre Moose Creek fire was about 25 percent contained as of Sunday afternoon, said Division of Forestry spokeswoman Sarah Saarloos. 

Fire officials on Sunday upgraded the size estimate from 216 to 300 acres, due more to better mapping than any actual growth of the fire, she said.

A map depicting the size and containment of the Moose Creek fire burning in Mat-Su on Oct. 16, 2016. (Alaska Division of Forestry)
A map depicting the size and containment of the Moose Creek fire burning in Mat-Su on Oct. 16, 2016. (Alaska Division of Forestry)

About 50 firefighters are battling the fire, which is burning 12 miles north of Palmer and about 5 miles south of Sutton on a mix of state and private land to the north of the Glenn Highway. The fire is burning in tall grass and deciduous hardwood forest. 

No structures were threatened as of Sunday evening.

"The threat decreased due to us being able to get 50-plus personnel and firefighters and being able to keep the spread of the fire from getting closer to homes," Saarloos said.

The fire was pushed by strong winds, blooming from just about 10 acres at 2 a.m. Saturday to the more than 200 acres reported by that evening, and posing a challenge for firefighters working to keep the fire within containment lines. Around 6 p.m. Sunday, a 3-acre flare-up prompted firefighters on the ground and helicopters in the air to act quickly. 

"In an effort contain the flare up, managers temporarily shifted firefighters from more-secure parts of the fire perimeter to bolster initial attack efforts," the Division of Forestry reported. "Firefighters are also contending with multiple spot fires popping up as a result of embers being carried by the wind."

Winds were gusting to 40 mph Sunday, forestry officials said.

The low temperatures of late fall were also creating difficulties.

"Several hoses and water tanks placed in strategic locations for hose and bucket work froze overnight due to below-freezing temperatures," the Division of Forestry reported.

Firefighters will continue to contend with gusty winds for at least the next day.

"The winds will keep fanning the flames," said National Weather Service meteorologist Joe Wegman. "The good news is there isn't expected to be much direct wind change, they'll stay out of the northeast."

Predictability makes conditions safer for firefighters, he said.

Conditions are dry and dangerous in the Mat-Su, Saarloos said. Several other small fires flared up in the region Sunday but were quickly put down by firefighters.

Downed power lines sparked two additional fires Sunday afternoon, according to Patty Sullivan, public affairs director for the Matanuska-Susitna Borough. Another fire was reported around 7:30 p.m. in the area of the Butte, down a trail off Plumley Road. That fire was the result of a landowner burning debris piles and firefighters were en route, Sullivan wrote.

"Not having any snow on the ground, it has left all this dry, tall grass available and if there's any spark it'll catch the dry grass on fire," Saarloos said.

Fire investigators believe the Moose Creek blaze was the result of an escaped debris burn but haven't released more information on who was overseeing the burn, Saarloos said.

Ben Anderson contributed to this report.