DENVER -- A Colorado woman is missing in Nepal on a trek in the Himalayas.

Aubrey Caroline Sacco, a 2009 Colorado-Boulder graduate whose parents live in Greeley, had been in south Asia for five months, teaching yoga and traveling.

The 23-year-old e-mailed her parents on April 20 just before beginning a seven- to eight-day hike in Langtang National Park, near the Tibetan border. She planned to make the trek alone and failed to check in after she was supposed to finish the trek.

She has a ticket for a May 15 flight home, but her father is worried.

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

The young woman was hiking alone without a guide or porter. There were not many other backpackers in the area because it was end of the trekking season.

The police chief in the Rasuwa area, Om Bahadur Rana, said police teams were searching the trekking route and interviewing inn owners and villagers. Word has been sent to local monasteries, which are often visited by foreign trekkers.

Rana said the teams are searching for clues up to 300 feet on either side of the mountain trail. Police sniffer dogs will also join the search, he said.

Rana said Sacco had signed in before entering the Langtang conservation area as required on April 20. But she never signed out and nobody saw a woman fitting her description leave the area, he said.

The search was unable to begin sooner because mass protests on May 1 and a general strike imposed by the Maoist former rebels shut down all transport in Nepal until May 7.

Information about the missing woman was received only after the strike was over and a search was immediately ordered, police said.

Sacco called his daughter "one tough cookie."

The family has contacted the U.S. Embassy, the Nepali government, and local newspapers, hoping to find someone who might have seen her along the route. Sherpas and local climbing clubs have also been notified to look for the woman.

A Facebook page has also been created by a relative to share information on the search for Sacco.

Thousands of Western backpackers visit during the spring season to hike in Nepal, home to dozens of popular mountain trails as well as Mount Everest, the world's highest peak.