Chinese President Hu Jintao urged rescuers in the southwestern province of Sichuan to race time to save lives, days after the most destructive earthquake to hit modern China, Reuters reported.
China has put the known death toll at over 22,000 but has said it expects it to exceed 50,000. About 4.8 million people have lost their homes and the days are numbered in which survivors can be found.
"Although the time for the best chance of rescue, the first 72 hours after an earthquake, has passed, saving lives remains the top priority of our work," Hu told distraught survivors just over a week after a jubilant China celebrated the Olympic torch reaching the summit of Mount Everest.
In earthquakes elsewhere in the world, survivors have been found a week or more after the disaster. In Baguio in the Philippines in 1990, a cook was found alive after two weeks in the rubble of a shattered hotel.
"Quake relief work has entered the most crucial phase," Hu said. "We must make every effort, race against time and overcome all difficulties to achieve the final victory of the relief efforts."
Many survivors were found on Friday, including six miners who took shelter in a pit for 88 hours, Xinhua news agency said.
Xinhua said 33 people were dug out of the rubble in Beichuan, one of the worst-hit areas, still alive.
Premier Wen Jiabao, also visiting the region, said the 7.9 magnitude quake was "the biggest and most destructive" since before the Communist revolution of 1949 and the quick response had helped reduce casualties.
Wen was comparing the disaster with the 1976 tremor in the northeastern city of Tangshan, which killed up to 300,000 people.
But as the weather gets warmer, survivors were increasingly worried about hygiene and asking questions about their longer-term future.
"What we don't need now is more instant noodles," said truck driver Wang Jianhong in the city of Dujiangyan. "We want to know now what will happen with our lives. We're not impatient but we need to know something."
In Beichuan, thousands of homeless flooded out of mountains into the city of Mianyang, many put into military trucks and taken to a refugee centre.
"It was really bad up there," farmer Dian Minggui said. "The whole mountain changed shape and all the homes are toppled."
Li Xinshen, 70, fled with relatives, walked for 10 hours from the village of Xuanping to Mianyang.
"Only today on the road out did we see soldiers walking up," she said. "Not one rescue worker came up to handle us."
Anger has been mounting at the large number of schools which collapsed and there is concern about the safety of a number of dams and reservoirs which have been weakened by the quake.
In Sichuan and neighboring Chongqing, at least 17 reservoirs have been damaged, with some dams cracked or leaking water. Several are on the Min River, which tumbles through the worst-hit areas between the Tibetan plateau and the Sichuan plain.
The country is also on precautionary alert against possible radiation leaks, according to a government website.
China's chief nuclear weapons research lab is in Mianyang, along with several secret atomic sites, but there are no nuclear power stations.
China has sent 130,000 troops to the disaster area, but roads buckled by the quake and blocked by landslides have made it hard for supplies and rescuers to reach the worst-hit areas.
Offers of help have flooded in. The first foreign rescue teams, from Japan, Russia, Taiwan, South Korea and Singapore have arrived in Sichuan province.