The Hilltop Fire near Lucky Peak Reservoir, which was reported at about 5 p.m. Tuesday, was human-caused, the Bureau of Land Management said.
The exact cause of the fire had not been determined by Wednesday morning, BLM spokeswoman Mallory Eils said. The fire burned about 400 acres of grass and sagebrush between Idaho Highway 21 and Lucky Peak.
But BLM crews expect to have the blaze contained by noon Wednesday, Eils said. Originally, firefighters thought the fire would be contained Tuesday night, but hot temperatures predicted for Wednesday caused officials to push the estimated time of containment back, she said.
BLM still expects the fire to be under control by 6 p.m. Thursday.
Steep terrain and winds caused the fire to grow quickly. Smoke from the fire lingered in the Boise area Wednesday morning, and officials said residual smoke could remain while interior pockets continue to burn and while firefighters conduct burnout operations to secure the fire lines.
At one point, the BLM said, the Boise Fire Department provided structure protection for a home in the area. Those resources were later released.
Numerous firefighting resources were dedicated to the fire, including six fire engines, three bulldozers, two water tenders, two helicopters, three air tankers and two hand crews.
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