A five-acre wildland fire on the northwest shore of Wild Horse Island in Flathead Lake is under control after flaring up Wednesday afternoon from an unattended campfire.

A 20-person crew worked through the night, bringing the wind-driven fire to 50 percent containment by Thursday afternoon, according to T.C. Camel, a fire prevention specialist with the Confederated Salish and Kootenai Tribes.

“It’s boring now,” Camel said, but noted that the crew would likely remain on the fire through the weekend. “On their side where it is, there’s a lot of rocks, and it’s going to take a lot of mop-up.”

Campfires are illegal on Wild Horse Island, and Park Manager Dave Landstrom said the rapid spread of the fire along the island’s shore demonstrated why.

“Because it’s an island, fire response is much more complicated than it would be anywhere else,” he said. “It’s quite an arid location, as opposed to some of the mainland sites. It sits out there and takes a lot of sun, a lot of wind.”

He added that because the campfire was on the lower part of the wooded island, the flames spread quickly uphill. Most fires he has seen at the location result from lightning strikes, which tend to be spotted and responded to more quickly.

Montana Fish, Wildlife and Parks will take the lead on the investigation if the agency gets any leads. Those with information about the campfire can provide it anonymously by calling 1-800-TIPMONT.

Boats from the Confederated Salish and Kootenai Tribes Fish, Wildlife, Recreation, and Conservation Department, the Lake County Sheriff’s Department and Lake County Search and Rescue responded Wednesday by ferrying crews over to the island. Two planes dropped retardant on the flames, and one helicopter responded by dropping water.

On Thursday, only the 20-man crew remained on the fire, reinforcing fire lines. Camel said there were no injuries and no structures damaged or threatened by the fire.

Reporter Samuel Wilson can be reached at 758-4446 or swilson@dailyinterlake.com.