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A frantic search was underway Thursday for three sisters who vanished while backpacking in the Wyoming wilderness, authorities said.

The sisters, originally from Milwaukee County, Wisconsin, left for their extended camping trip in Grand Teton National Park on June 28 and were supposed to return home Tuesday, the Teton County Sheriff's Office said.

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A website devoted to finding the trio identifies them as Megan Margaret Andrews-Sharer, 25; Erin Andrews-Sharer, 22; and Kelsi Andrews-Sharer, 16.

Sisters Erin, 22, Megan, 25, and Kelsi Andrews-Sharer, 16, went camping in Teton National Park in Wyoming. They were reported missong on July 7. Courtesy Andrews-Sharer family

According to their family, the women last used their cellphones on June 30, about 15 miles south of the resort town of Jackson.

Their black Saturn Vue with Wisconsin license plates was found at a trailhead at the nearby Bridger-Teton National Forest on Wednesday, officials said.

About 60 people are expected to help scour the winding trails, deep canyons and dense vegetation of the Wyoming backcountry. Ground crews, dog teams, personnel on horseback and a helicopter were being used Wednesday.

Authorities said the sisters are experienced backpackers and had the right camping gear with them for the multi-day excursion.

"They are healthy, fit young women and were well prepared for this trip," Teton County Sheriff Jim Whalen said in a statement. "However, despite their experience in the backcountry, they may have simply made a wrong turn."