MIANYANG, China - Heavy rain yesterday slowed Chinese soldiers as they raced against time to prevent the most dangerous of 34 lakes created by landslides from the May 12 earthquake from bursting its banks.

More than 158,000 people have been evacuated downstream of the Tangjiashan "quake lake" near Beichuan, in hard-hit Sichuan province, and five million more who live in Mianyang City have been participating in evacuation drills in recent days as the lake's waters continue to rise.

About 600 soldiers worked through the night to dig a channel that would provide a controlled flow for the water, but helicopters that had been ferrying equipment and fuel to the site were grounded by the weather in midafternoon, state media reported.

Soldiers using earth-moving equipment have succeeded in digging a trench 50 yards wide and 300 yards long. But Liu Ning, chief engineer of the Ministry of Water Resources, said they also cleared an emergency retreat path for themselves yesterday in case the water rises too quickly and they have to abandon the huge excavation effort.

Recovery efforts in Beichuan county were set back also when a stockpile of chemicals used to disinfect the rubble of buildings ignited.

The fire engulfed the area in heavy smoke and dangerous fumes, state television reported. At least 800 people in the area were evacuated and 61 soldiers were injured.

There was more official acknowledgment yesterday that corrupt construction practices may have contributed to the collapse of dozens of school buildings that killed at least 9,000 children.

The government-run New China News Agency said Lin Qiang, vice inspector of the province's educational department, had withdrawn as an Olympic torchbearer to underline his belief that the school buildings might have better withstood the quake "if we educational officials hadn't left loopholes for corruption."

Facing parent anger over the children's deaths, a government team of building engineers began inspecting at least one of the devastated schools.

At Fuxin No. 2 Primary School in Mianzhu City, the investigators took photos of the ruins and samples of the tons of concrete and bricks that crushed to death 127 students, according to a parent who is monitoring the situation.

Even as officials continue the task of tallying confirmed deaths - 68,516 so far, and expected to rise to at least 80,000 - they are beginning to calculate the quake's economic impact.

The State Information Center estimated that the earthquake caused $86 billion in losses, more than triple the impact of a severe snowstorm in February that paralyzed portions of the nation's transportation network.

Premier Wen Jiabao has said the government would allocate more than $10 billion this year to begin reconstruction.

While most of Sichuan's industrial production facilities are in areas unaffected by the quake, the province does produce 9.2 percent of the nation's grain and 11.6 percent of its pork, so economists worry the quake will worsen food prices.

Sichuan's tourist industry also suffered a big blow. Not only were some scenic spots destroyed, including most of the 2,000-year-old buildings at Erwang Temple, but the giant-panda reserve in Wolong is struggling.

Shortly after the quake, reserve workers hiked into the forests to check on the pandas. They found no dead pandas, but dangerous conditions have prevented them from making a new check, the New China News Agency reported.

The Associated Press reported that the reserve is considering moving to a new home.

"What I'm worrying about are secondary disasters, such as severe aftershocks," Zhang Hemin, chief of the Wolong Giant Panda Reserve, said by phone. "The road is easily blocked by rocks falling from the mountain. There would be no way to get the food in."