DULUTH — The wildfire smoldering in the Boundary Waters Canoe Area Wilderness since last week was caused by a human, officials with the Superior National Forest said.

The Forest Service detected the Spice Lake Fire June 13. On Monday, it was 80% contained within created fire perimeters and 22 acres in size. Spice Lake is east of Knife and Kekekabic lakes and southwest of Seagull Lake, about 10 miles west of the Gunflint Trail.

Federal fire investigators visited the area Saturday to determine a cause, but declined to speak about the investigation. Nationally, 85% of wildfires are started by humans, according to the National Park Service.

Although the area didn't receive rain over the weekend, fire activity has been minimal, the Forest Service said. A 19-person hotshot crew has finished its work but more than a dozen firefighters continue to work.

A closure order for the area, effective Friday, prohibits visitors on about 100,000 acres of trails, portages, rivers and lakes surrounding the fire, including a portion of the Kekekabic Trail. It affects 80 campsites, and popular entry points including Moose Lake, Saganaga Lake, Seagull Lake and Snowbank. Affected permit holders and outfitters have been notified of the closure order.

The Forest Service said the closure area is so large because "the capacity for extreme fire behavior and excessive fuel conditions all lend to a large fire growth potential."

Campfire restrictions in the Superior National Forest, which includes the Boundary Waters, remain. All businesses along the Gunflint Trail are open, the Forest Service said.