Heavy rain over southwest China on Wednesday is likely to interrupt relief efforts and raise the risk of reservoir breaches in earthquake-stricken areas, where tents have become the most-wanted item.

Thousands of aftershocks and a forecast of more rain compounded the difficulties for military, government and private workers trying to deliver aid and ensure millions get shelter as the focus of relief work turned inevitably from rescue to relief.

New survivors were still being found in the rubble on Tuesday, eight days after the disaster. One was a 60-year-old woman who Xinhua said had survived on rainwater.

But a Japanese rescue team pulled out of the area on Tuesday after failing to find anyone alive under the ruined buildings and will be replaced by a medical team.

Officials said China needed up to 3 million tents to house an estimated 5 million people left homeless by May 12's 7.9-magnitude quake in Sichuan province.

Vice provincial governor Li Chengyun on Tuesday appealed other parts of China and the outside world to donate tents.

Premier Wen Jiabao ordered the supply of 250,000 temporary housing units -- simple steel structures normally used by construction workers -- to the quake area by June 30 and the number should reach 1 million in three months, state media said.

Many residents of Chengdu, the provincial capital hit by a persistent drizzle on Wednesday, spent the night in tents, fearful of building collapses.

Nearly the whole population of Shifang, a small city near Chengdu, slept outside on Tuesday night despite the rain. In the countryside, many farmers now live in encampments of makeshift shelters with their homes too damaged or too unsafe to live in.

"SECONDARY DISASTERS"

"We don't know when it will be safe to go back inside our houses but I don't know how long we can put up with living outside either," farmer Wu Xingyao said under the cover of plastic and tarpaulin.

More than 40,000 people have been confirmed dead and the government said it expected the final death toll to exceed 50,000. More than 247,000 were injured.

At a cabinet meeting on Tuesday, Wen warned of the threat of "secondary disasters", ordering experts to inspect dams and reservoirs on 24-hour patrols with more heavy rain forecast.

Wen said damaged dams must open floodgates to run at low or even empty water levels and the dozens of "barrier lakes" formed by numerous landslides blocking river flows must be monitored.

In Qingchuan county, where more than 2,670 people have died in the quake, troops evacuated some 9,000 residents on Tuesday after huge cracks appeared on the top of a mountain, Xinhua said.

In Beichuan, the devastation has been so complete that the government is considering abandoning the county seat and rebuilding it elsewhere, making the ravaged town a memorial, local media said. Over 8,600 people were killed in the county.

A total of 32 civilian "radioactive sources" had been buried under debris after the quake, but 30 of them had been recovered, Xinhua said. It did not give details or specify the risk.

China started three days of national mourning on Monday, with flags raised at half-mast and public entertainment suspended.

On Tuesday, thousands gathered in Tiananmen Square to cheer on China just 80 days before the start of the Beijing Olympics in what was supposed to be a joyful countdown to the Games.