MORE than a million people were on the move last night to escape the new danger of floods in remote areas blocked by earthquake debris in China’s western Sichuan province.

Soldiers of the People’s Liberation Army were seen carrying old folk in their arms out of the town of Beichuan, while the able-bod-ied fled on foot or in vehicles.

Police warned that a river choked with landslide rubble might burst its confines at any moment and inundate the town.

Some survivors were believed to be still clinging to life under Beichuan’s collapsed buildings, from where a 52-year-old man was rescued after 117 hours entombed in the ruins.

About 50 miles to the northeast, the authorities were trying to move hundreds of thousands of people from the county of Qingchuan, where rising water levels threatened to burst the banks of a lake.

According to a report on Hong Kong’s cable television network, an exodus of both civilians and military was in progress. The mass flight of earthquake victims came as China’s cabinet spokesman, Guo Weimin, said the confirmed death toll in last Monday’s quake had reached 28,881. The government expects the final figure to exceed 50,000.

It emerged yesterday that in one of the most harrowing incidents to be uncovered, more than 100 children trapped in collapsed classrooms had been overwhelmed by poisonous gas from a nearby chemical plant.

A cloud of ammonia from the plant in Yinghua, where workers died in a torrent of acid from burst pipes, drifted down a valley to Lau Sui middle and high school as staff and pupils were clearing bricks and concrete to free classmates.

Two pupils, Yang Li and Hu Ying, said they had started gasping for breath, unable to open their eyes. Another, Zhou Zhou, described children losing consciousness.

“The headmaster said to go in the opposite direction from the factory,” she said. “We had to step over bodies.” A teacher confirmed the death toll.

This weekend, reverberating shocks and landslides posed a continuous hazard that was intensified around the dams and reservoirs carved out of the granite mountains in Sichuan, one of the most active earthquake zones in the world.

The feats of soldiers and helicopter pilots in the face of danger drew praise from Chinese victims and foreign tourists rescued from disaster. In contrast to the inertia of the reclusive Burmese military junta after the cyclone of May 3, the Chinese state responded by mobilising 130,000 troops, sending rescue teams, organising medical aid and scrambling more than 100 helicopters to the misty valleys.

Domestic and foreign media coverage of the disaster has been extensive, compared with the funereal silence that enveloped the 240,000 dead of the Tang-shan earthquake of 1976, China’s last seismic catastrophe.

Like politicians in most countries, President Hu Jintao and his premier, Wen Jiabao, flew in to offer comfort and support, all televised on the evening news to assure public opinion that everything possible was being done.

China has welcomed specialist earthquake rescuers from Japan, its wartime foe, while teams from Singapore, South Korea and Russia also got to work yesterday. Two giant US Air Force cargo planes were en route as well, bringing tents, lanterns and meals. A jumbo jet loaded with aid from the democratically ruled island of Taiwan was accepted with good grace. However, British experts were still waiting for visas in Hong Kong.

The scale of the task is daunting: hospitals in Sichuan have taken in 116,460 patients, according to the state news agency, Xinhua.

If the immediate demands are humanitarian, however, the implications of the calamity are also political and diplomatic.

As national grief turns into public questioning, the Communist party leadership has issued strict guidelines to the Chinese media to channel coverage in a “positive” way. The media and internet commentators have already criticised official corruption in building standards that turned schools into deathtraps.

Inevitably, many people, echoing victims of Hurricane Katrina in the United States, complained of help that came too little and too late.

The earthquake has also emboldened a popular Chinese tradition of irreverence for leaders combined with pride in the ordinary people. “Let’s not sing the praises of leaders while the whole nation is mourning,” said one daring netizen on the Xinhua website.

The political risk for the Communist party is likely to intensify as hard questions are asked about the central planning policies that put so many people and industrial plants in an earthquake zone. The factories and towns hidden away in Sichuan’s valleys are the legacy of one of Mao Tse-tung’s least-known but most grandiose projects.

Fearing a nuclear attack by the United States or the Soviet Union, Mao ordered the construction of a redoubt to shelter China’s defence industry. He gave the task to Deng Xiaoping, a native of Sichuan. Starting in the 1950s, Deng built an impregnable arsenal hidden by the mountains.

He built tunnels, dammed rivers, threw railways across gorges, drove highways through the wilderness, installed power stations, nuclear weapons plants, steelworks, chemical factories and arms workshops, some hidden in caverns. Standards were shoddy and hundreds died as “worker-martyrs”. The project was bigger than the Roosevelt New Deal or Stalin’s first five-year plan and it consumed between 40% and 45% of China’s capital budget from 1965-75.

It was all done in total secrecy. “Populations were moved from Shanghai and Tianjin into towns that appeared on no maps,” wrote Harrison Salisbury in his dual biography of Mao and Deng. Nobody dared question either man about the decision to locate these industries and all their people along an active tectonic boundary.

Times have changed in China, however, and one immediate policy question is whether these vulnerable industries and towns should ever be rebuilt.

The government will face an immediate challenge to “social stability” in housing and caring for thousands of homeless families. More than 4m homes were damaged or destroyed. Water supply has been cut off in 20 cities and counties. Tent camps are springing up to shelter displaced families. Just north of Chengdu, the provincial capital, 2,000 people are occupying the town square in Shi-fang.

A year marked with the lucky Chinese number eight and to be crowned by the Beijing Olympics has so far been scarred by ill fortune: destructive snowstorms, the Tibetan uprising - and now the most catastrophic earthquake since 1976. In Chinese culture, such omens commonly herald the fall of a dynasty.

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