ISABELLA, Minn. – Mark and Laura Hochhalter scanned the horizon from the edge of Greenwood Lake on Monday afternoon as thick, acrid smoke billowed across the sky.

The Stacy, Minn., couple has a remote cabin a few miles west of the lake in the middle of the Superior National Forest, and they drove up fearing that it was in the path of the fast-moving blaze, measured at 2,000 acres by Monday evening.

"It looks like it's moving away, but that can turn overnight," Laura Hochhalter said.

Minutes before, a helicopter dropped fire retardant on bright flames torching trees along a power line corridor as the fire leapt closer to Hwy. 2.

Residents of homes and cabins in the McDougal Lake area were told to evacuate Monday as the Greenwood fire, which began Sunday afternoon, grew rapidly amid gusty winds and bone-dry weather. Sections of Hwy. 2 and Minnesota Hwy. 1 were closed, as were nearby trails, boat launches and campgrounds.

Law enforcement and emergency personnel went door-to-door notifying residents if they are in an evacuation area and posted notices. About 75 residences have been affected, according to the Forest Service.

The fire is "torching and spotting," said Jeb Backe, an incident commander for the Superior National Forest, meaning trees are igniting and flaring up and sparks are being carried by the wind and starting new fires.

Top priorities are public and firefighter safety, along with protecting structures, he said, but "our biggest concern is new starts, as we're limited on resources."

He asked people to abide by the county's burning ban, which includes private property. Firefighters are attacking the blaze from the air and the ground, dropping water from planes and starting containment lines where they can, a task made more difficult because of the inaccessibility of the forestland. Fire officials expect a northern path and encourage people to stay out of the area.

The cause of the fire is unknown, Backe said.

Superior National Forest fire manager Nick Petrack said in a social media video update that the fire's behavior is "extreme."

"With the current weather we expect the fire to remain very active in the next three to four days," he said. With mixed conifers fueling the blaze, making it challenging for crews to suppress, more fire personnel are expected to join in the next day, he said.

Gov. Tim Walz authorized Minnesota National Guard support for northern wildfires on Monday. Along with the activation of 16 soldiers and two airmen, the St. Paul-based 2-147 Assault Helicopter Battalion is sending two Black Hawk helicopters and two Heavy Expanded Mobility Tactical Trucks. The Duluth-based 148th Fighter Wing is sending a fuel truck.

An air quality alert has been issued for Lake County through Tuesday afternoon.

The Greenwood fire is one of many burning in the northern half of the state. Several within the Superior National Forest and the Boundary Waters Canoe Area Wilderness have been contained, but new fires, like the Whelp and John Elk fires northeast of Isabella, continue to crop up. The Quetico Provincial Park fires closest to the Minnesota border remain active and monitored by the Forest Service.

Staff writer Alex Chhith contributed to this report.