BOISE, Idaho (AP) — A wildfire in east-central Idaho burning in an area where there hasn't been a wildfire in 80 years is threatening historic gold mines and fire lookouts, officials said Thursday.

The fire in the Salmon-Challis National Forest grew to 9 square miles (23 square kilometers).

"The fuels we have here are running 40 to 50 percent snags (dead trees)," said fire spokesman Norm Rooker. "Along with that, we have a bumper crop of understory cheatgrass." Cheatgrass is an invasive species that dries out and becomes fire-prone, fueling flames.

The area includes the historic Rabbitfoot Mine, near where the fire started with a lightning strike on Aug. 2. Rooker said historic fire lookouts could be in peril. The Salmon-Challis National Forest has six staffed lookouts.

The fire is not contained and isn't expected to be for two months, he said. Roads and trails in parts of the Salmon-Challis National Forest have closed to the public. About 360 firefighters are at the blaze and have been trying to establish fire lines in the rugged area, Rooker said, but have had to retreat several times.

"We're attempting to establish and anchor point that we can build (fire lines) off of and know the fire won't hook around and come up behind us," he said.

He also said winds up to 45 mph (72 kph) this weekend will likely cause many of the dead trees in the area to fall. "So it makes it very dangerous for our firefighters to get in and work," he said.

Meanwhile, firefighters made good progress in other areas of the state.

In central Idaho, a wildfire grew to 101 square miles (262 square kilometers) on Thursday, but officials said it's 68 percent contained with full containment expected on Sunday. The Sharps Fire burning timber and grass is about 6 miles (10 kilometers) east of Bellevue.

"Things are looking really good," said fire spokeswoman Kim Osborn. Firefighters "are doing a lot of good work and things are moving along as we expected."

She said firefighters are strengthening fire lines in anticipation of high winds this weekend. No structures have been lost, but some federal lands in the area have closed to the public.

In west-central Idaho, the Mesa Fire has consumed 53 square miles (137 square kilometers). That fire in timber and grass is 57 percent contained.

Fire spokeswoman Anna Ball said crews have been steadily increasing containment and strengthening fire lines ahead of 45 mph (70 kph) winds expected Friday.

Firefighters are "working on getting all those lines secure so they can hold them with the weather coming in," she said.

The fire started on July 26 on private land, Ball said, and two homes and three outbuildings were destroyed early in the fire. But she said no structures have been lost since and there have been no firefighter injuries.

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