Statistics from past earthquakes show victims have survived up to nearly a fortnight under rubble.
There was a burst of elation in ruined Beichuan, when one woman was found alive.
Wang Hongguo, head of the rescue team, said she had found her under a mass of concrete. "We had to pull her out very gradually. She looked quite sturdy, so she might pull through," Wang said.
Rescuers also found a 50-year-old woman alive in the wreckage of a residential building at the Tianchi Coal Mine.
But seven days after the quake, rescuers mostly had the gruesome job of recovering decomposing bodies. Dozens of bodies were pulled from the rubble in Beichuan on Monday, and rescuers scattered lime and splashed disinfectant to prevent disease.
Even with hundreds of troops poring over the wreckage, some using specialised equipment and sniffer dogs, others carried on the search themselves.
Farmer Wang Hongchen and his wife Chen Guangfen scrambled over hundreds of metres of rubble to look for their son, who worked as a mobile phone repair man in the town.
"I think there's still hope. He worked on the first floor, so if he was lucky there would have been space for him to survive," Wang said, in between shouting out his son's name over the ruins.
"There's nothing I want more than to find him alive," added Chen. "Other people who know their relatives have died can call this a memorial day, or a funeral, but not me yet."
Officials have tried to keep people from the area because of aftershocks and a build-up of water in blocked rivers. Xinhua said the most dangerous mass of water was only about 3 km (2 miles) upstream from Beichuan.
Rescuers had yet to reach all the stricken villages, Xinhua reported. By late Sunday, 77 villages were still cut off.
China says it expects the final death toll to exceed 50,000.
Huge tent cities have sprung up in Sichuan to accommodate about 4.8 million people who lost their homes. A Foreign Ministry spokesman appealed to the international community to provide more tents, Xinhua reported.
Donations from home and abroad have topped 6 billion yuan (440 million pounds).
