Three geological technicians from Shaanxi Geological and Mineral Resources Development Corporation have been missing for 15 days and an unmanned aircraft is about to become involved in the search effort.

Bai Linke, deputy general manager of the company and the search work commander, said the missing technicians went to Hoh Xil, Qinghai province, in Northwest China, on Feb 17 for a project survey and did not return as planned on Feb 19.

Yang Nengchang during a field exploration trip. [File Photo]

It is believed that the men went missing in the region of Chibuzhang Lake, in northern Tibet, which has an elevation of 4,900 meters to 5,000 meters, Bai said.

Search teams with more than 1,000 people were sent from Shaanxi and Qinghai provinces, and from the Tibet autonomous region to search more than 1,000 sq km around the lake.

Because the ice on the lake was melting, search teams and local herdsmen speculated that the three technicians may have driven on the ice and fallen into the water.

"Speculation is speculation. We will make a 100 percent effort to search for the missing people, even if there is only 0.1 percent of hope," Bai said.

The three missing technicians - Yang Nengchang, 36; Rong Hao, 23; and Gao Chongmin, 53 - were said to have been driving a Cherokee off-road vehicle and had food for seven to 10 days, as well as GPS, radio and satellite phone.

In addition to the ground search, searchers had planned to use helicopters, but weather conditions were too poor.

The brother-in-law of Yang Nengchang, one of the three technicians of Shaanxi Geological and Mineral Resources Development Corp missing in Hoh Xil, Qinghai province, comforts Yang's wife on Wednesday. She has been crying every day while reading the disappointing search reports. [Ye Yuan / for China Daily]

"We will continue our effort of ground searching and will also ask relevant departments to help us by satellite remote sensing and unmanned aircraft searching," Bai said.

Meng Junhai, geological expert with Qinghai Province Third Geology and Mineral Exploration Institute, who took part in the search, said the most severe difficulties were cold weather and high altitude.

"The terrain in the region is very complicated and the ice on the lake surface is very thin in some parts," Meng said.

Shen Anbin, deputy manager of the company's branch firm in which the three missing technicians worked, told China Daily on Monday that 15 family members of the missing men were staying in Xi'an, capital of Northwest China's Shaanxi province and headquarters of the company, and were being taken care of by company staff and two doctors.

"The three families are waiting for their missing relatives and are in relatively stable physical condition," Shen said.

Rong Li, the older sister of Rong Hao, said she was very worried about her brother and the other technicians. She said family members understood that the search teams had made a great effort.

Zhang Jingji, director of the company's information center, told China Daily that company general manager Zhao Tingzhou led the fifth search team to the frontline command on Sunday to carry out a new round of searching.

"It was dangerous for the missing people as 15 days have passed and the search teams will continue to looking for them. We will also pay great attention to ensuring the safety of the searchers because the conditions are so harsh," Bai said.

The writer can be reached at malie@chinadaily.com.cn.