A helicopter receives a safety check on June 1 upon returning from a search mission for a Mi-171 transport helicopter that crashed Saturday afternoon while transferring people from quake-hit Maoxian County, southwest China's Sichuan Province, to a safe place. [Photo:xinhuanet]

A helicopter in flight is searching for a Mi-171 transport helicopter that crashed Saturday afternoon while transferring people from quake-hit Maoxian County, Sichuan, to a safe place. [Photo:xinhuanet]

More than 4,000 military personnel Sunday were searching for survivors of a military transport helicopter that crashed with four relief workers and 14 injured quake survivors near Yingxiu township in Sichuan province on Saturday.

The Mi-171 helicopter was returning after carrying a team of epidemic prevention experts to Lixian county and picking up the injured when it encountered strong turbulence and fog, and crashed at 2:56 pm, military sources said.

President Hu Jintao, who is overseeing quake relief operations in neighboring Shaanxi province, ordered local authorities to conduct a thorough search for the survivors.

On Saturday, a day before International Children's Day, Hu visited a temporary school in quake-hit Hanzhong, Shaanxi province, and spent time with the children there.

He told vice-chairman of the Central Military Commission Guo Boxiong to fly to the frontline to direct the operation.

Guo has already reached Chengdu, capital of Sichuan province, and held a meeting Sunday morning, instructing rescue workers how to conduct the operation.

But the rescue teams have not been able to identify the exact spot of the crash. That's why it's difficult to say if there are any survivors.

Chinese military officers discuss a plan for the search of the crashed helicopter at Fenghuangshan airport in Chengdu, capital of southwest China's Sichuan Province, June 1, 2008. A military transport helicopter engaged in quake relief work near Yingxiu Township, Wenchuan County in Southwest China's Sichuan Province crashed on Saturday afternoon, according to military sources. [Photo:xinhuanet]

Teams of soldiers arrive at Wenchuan County in Sichuan Province on June 1 to search for a Mi-171 transport helicopter that crashed Saturday afternoon while transferring people from quake-hit Maoxian County, Sichuan, to a safe place. [Photo:xinhuanet]

Teams of soldiers arrive at Wenchuan County in Sichuan Province on June 1 to search for a Mi-171 transport helicopter that crashed Saturday afternoon while transferring people from quake-hit Maoxian County, Sichuan, to a safe place. [Photo:xinhuanet]

Teams of soldiers arrive at Wenchuan County in Sichuan Province on June 1 to search for a Mi-171 transport helicopter that crashed Saturday afternoon while transferring people from quake-hit Maoxian County, Sichuan, to a safe place. [Photo:xinhuanet]

Editor: Yan