CASPER (WNE) — A fire burning in the Medicine Bow National Forest west of Laramie nearly doubled in size on Sunday to almost 14,000 acres and prompted multiple evacuations.

The Rambler, Rob Roy and Keystone areas have all been evacuated due to the Mullen Fire, Gov. Mark Gordon tweeted Sunday morning.

On Saturday afternoon, the fire had moved to within a mile of 25 summer cabins near Rob Roy Reservoir, Gordon wrote in a separate tweet.

The Mullen Fire has grown quickly since it ignited Thursday. On Friday, it increased to 644 acres. By Saturday, that number had risen to 7,500.

“This is a major fire, folks,” the Medicine Bow National Forest posted in a tweet on Saturday afternoon.

Strong and shifting winds prompted crews on Saturday to pull back firefighting resources for safety reasons, authorities said. Those conditions also prompted officials to pull aerial resources from the fire.

In response to “extreme fire behavior,” authorities issued a closure order that covered much of the southern Snowy Range in Albany and Carbon counties, according to a press release from the U.S. Forest Service.

Authorities on Sunday told residents in the Centennial Valley to prepare for possible evacuations.

In a statement, the Forest Service said it was actively investigating the fire’s cause. Officials had identified the area where the blaze originated and found preliminary information indicating the fire might have been caused by humans.