Most of the survivors have to stay in the open area overnight after a 7.1-magnitude quake toppled houses, cut off power and first-aid materials supply in northwest China's Qinghai Province Wednesday while rescuers face difficulties in searching for the buried.

Rescuers have set up more than 40 tents for survivors in the Gyegu Town, near the epicenter in the Tibetan Autonomous Prefecture of Yushu in southern Qinghai. But the effort seems far less than enough for the area inhabited by some 100,000 population.

Many people sought temporary shelters in buildings that remained unaffected by the tremor.

In the yard of Yushu's Sports Committee, nearly 1,000 people were sitting or lying on the ground in sheer darkness. Some wrapped themselves up with quilts taken out from the debris.

Some brought their own tents and others turned on the lights of motorcycles.

"I'm hungry and thirsty, we've been waiting for help since the morning," said Zhaxi Toinzhub.

The woman said her three children were still buried in the rubble.

The National Meteorological Station forecast Wednesday that temperatures at night may hit minus 3 degrees Celcius at night and 15 degrees Celcius in the daytime in the coming days.

The town would see strong winds and sunny weather in the coming days, providing favorable conditions for rescue operation.

The town is located in a remote area in Qinghai and the quake and ensuing landslides have damaged roads, causing great difficulties for resucers and, especially, machines from outside to enter the region.

Rescuers had to dig with bare hands or iron sticks Wednesday, looking forward for the arrival of digging machines, said a rescuer surnamed Wang, who was working at a collapsed hostel.

The searching operation became even harder at night without lighting facilities, he said.

In addition, rescuers may easily get exhausted working at a place with an altitude of above 4,000 meters.

Thoudsands of rescuers and medical staff are rushing to Yushu from many regions of China, bringing machines, disaster-relief materials and medicines to the quake-hit town. Governments, organizations, enterprises and individuals are offering donations of money and materials to the region.

The quake, which struck Wednesday morning and was followed by a string of aftershocks, has left at least 400 people dead and 10,000 others injured. As many people are still buried under the rubble, the casualties may increase as rescue operations get intensified.