(CNN) -- Authorities asked people to evacuate 1,000 structures near a wildfire in Alaska's Kenai National Wildlife Refuge on Sunday as the blaze spread.
The Funny River Fire has been raging for almost a week in Soldotna, south of Anchorage, growing to engulf 140,000 acres by Sunday afternoon. Now, fire officials are worried recreational cabins and second homes where residents and retirees are spending the holiday weekend may be at risk, said Michelle Weston with the Alaska Interagency Incident Management Team.
The voluntary evacuation notice was issued for structures near the blaze on Sunday, Weston said.
So far, no structures have burned in the fire.
Earlier Sunday, emergency officials said windy weather was pushing the fire further into the refuge and away from homes.
Investigators said they suspect human action was the cause, but authorities were still investigating.
The containment was at 20% with 450 personnel fighting the blaze. The Air National Guard sent two helicopters to assist with water drops, in addition to the four helicopters performing aerial firefighting.