XINING - Rescuers in Northwest China's Qinghai province are making efforts to search for three geologists who went missing during a field trip to the remote Hoh Xil nature reserve almost two weeks ago.

The three geologists, 36-year-old Yang Nengchang, 53-year-old Gao Chongmin and 23-year-old Rong Hao, were reported missing on Feb 19, the day they were scheduled to return to their campsite from a three-day excursion, said a spokesman with the Qinghai provincial land and resources department.

All three geologists worked for a subsidiary of the state-owned Shaanxi Geological and Mineral Resources Development Corporation of Northwest China's Shaanxi province, said Shen Anbin, a company executive who is assisting the rescue efforts.

The geologists arrived in Hoh Xil last September for a survey that was scheduled to last until the end of April.

On Feb 17, they left for a field trip near Tripug Dratso, a lake area with a large expanse of wetlands and swamps, Shen said.

However, their colleagues and relatives have not heard from them since.

As of Thursday, rescuers had searched an area totaling 1,030 square km near Tripug Dratso and captured satellite images of the area in an effort to find the geologists.

However, Shen said the area was overcast when the satellite images were taken, which made decoding and data analysis more difficult.

Yang Langtao, a senior editor with Chinese National Geography magazine, said it would be unlikely for their vehicle to become trapped in the swamp during the winter.

"Their vehicle may have had a mechanical failure and left them stranded," he said. "It is also possible that their satellite phone was turned off."

Yang said their condition might be critical, as they only had enough supplies to last for about two weeks. The plateau region's tough winter climate may also pose problems, Yang said.

Hoh Xil, also known as Kekexili, is a reserve that encompasses China's largest area of uninhabited land. It is home to several species of endangered wildlife, including Tibetan antelopes.

The region became well-known following the release of the award-winning feature film Mountain Patrol by Chinese director Lu Chuan. It tells the true story of a journalist who joined a Tibetan volunteer patrol to pursue poachers trading Tibetan antelope skins in Hoh Xil.