University of Colorado-Boulder graduate Aubrey Sacco, 23, is missing in Nepal, failing to contact her family after a planned trek in the Himalayas.

Her parents, who live in Greeley, said their daughter has been in south Asia for the past five months, first teaching yoga and then travelling. Paul Sacco, her father, said they last received an e-mail from her on April 20, when she began a seven- to eight-day trek.

He said they expected her to be out of touch during the trek, which she made alone in the Langtang Valley just south of the Tibetan border. But they became worried when they hadn’t heard from her several days after she was expected to return, and news reports showed Maoists striking in Kathmandu.

“We’re very concerned, but I know she’s out there,” Paul Sacco said. “She’s one tough cookie. She’s my hero.”

He’s hoping that she heard about the demonstrations, which crippled the nation before ending on Friday, and decided to stay in the mountains. Her flight back to the United States is scheduled for May 15.

“She might be safe, but there’s no communication,” her father said. “If she doesn’t get on that plane, I’m going there to get her.”

He said she started out in Sri Lanka, where she worked for a month as a yoga instructor at a posh resort before travelling through India on what she considered a journey of self discovery to expand her knowledge of eastern philosophy.

“She is incredibly courageous and a free spirit,” he said.

The 2009 CU graduate, who earned degrees in studio art and psychology, has traveled extensively, receiving grants through CU for cultural photography studies in South America, Japan and south Asia.

Last year, she started the Campus Dance Project at CU, playing music on campus and encouraging students to dance along with her.

Her family is working with the U.S. Embassy, Nepali government, Nepali newspapers and sherpas in the search. Others also are looking along the route she took. She planned to follow the Lonely Planet guide.

Paul Sacco said he’s hoping that someone who recently returned from a trek in the Himalayas may have seen or talked to her, or at least could verify that people were extending their treks to avoid the demonstrations.

“If the word on the mountain was ‘Don’t go back to Kathmandu,’ that would make me feel a lot better,” he said.

To contact the Sacco family, e-mail csacco2700@gmail.com. A Facebook page  — titled “American Aubrey Sacco Missing” — also has been created to share information on the search.