Crews continued to fight a wildfire overnight and into Thursday morning in the Superior National Forest about 25 to 30 miles west of Tofte, Minn.

In an update on the forest's Facebook page, the Forest Service said aircraft dropped water on the fire Wednesday afternoon. Ground crews worked the fire, and cloud cover and rising humidity have improved conditions.

"Crews are engaging the fire again this morning and working to secure the edge. Light rain is falling over the fire area. We are working to get an update on the size," the agency added in its post.

Forest Service managers said the fire was spotted outside a prescribed burn worked by crews in the 72-acre Fry Unit, north of Hwy. 1, east of Fish Fry Lake and west of Little Isabella River Campground.

The Forest Service wrote in an email Wednesday that neither the size of the fire is known nor the threat to nearby structures.

The agency has several planned prescribed burns this spring to reduce dangerous fuel loads, some created by factors such as spruce budworm, which has killed off balsam firs.

The Forest Service burned 159 acres Wednesday in the Slim Lake South Unit northwest of Ely and Burntside Lake and partly within the Boundary Waters Canoe Area Wilderness. A BWCAW entry point and portage were closed during the burn. Crews recently finished a 390-acre burn off the Gunflint Trail.

Check back at startribune.com for updates. The Forest Service also posts news on the Superior National Forest's Facebook page.