By WILLIAM FOREMAN

CHENGDU, China _ A powerful earthquake toppled buildings, schools and chemical plants Monday in central China, killing about 10,000 people and trapping untold numbers in mounds of concrete, steel and earth in the country's worst quake in three decades.

The 7.9-magnitude quake devastated a region of small cities and towns set amid steep hills north of Sichuan's provincial capital of Chengdu. Striking in midafternoon, it emptied office buildings across the country in Beijing and could be felt as far away as Vietnam.

About 1,300 rescue workers and troops arrived Tuesday at the quake's epicenter, which had been cut off since the earthquake struck. The number of casualties there is not yet known.

Rain has compounded the difficulty of rescue efforts elsewhere. Premier Wen Jiabao, who flew to the region, said rain was forecast for the next several days.

The government was pouring in troops to aid in the disaster recovery. Xinhua said 16,000 were in the area and 34,000 more were en route.

Snippets from state media and photos posted on the Internet underscored the immense scale of the devastation. In the town of Juyuan, south of the epicenter, a three-story high school collapsed, burying as many as 900 students and killing at least 50, the official Xinhua news agency said. Photos showed people using cranes, mechanical hoists and their hands to remove slabs of concrete and steel.

The news agency reported on Tuesday that another 1,000 students and teachers were buried and feared dead when a high school collapsed in Beichuan county. The building was reduced to a pile of rubble two yards high, it said.

Buried teenagers struggled to break free from the rubble in Juyuan, "while others were crying out for help," Xinhua said. Families waited in the rain near the wreckage as rescuers wrote the names of the dead on a blackboard, Xinhua said.

Parents of the dead students built makeshift religious altars at the site, resting the corpses on any available piece of plywood or cardboard, and burning paper money and incense in a traditional honor for their child in the afterlife, according to NPR's Melissa Block.

The earthquake hit one of the last homes of the giant panda at the Wolong Nature Reserve and panda breeding center, in Wenchuan county, Xinhua said. But the agency reported that 60 pandas at another breeding center in Chengdu were safe.

In Gansu province, which neighbors Sichuan, a 40-car freight train derailed and caught fire in the earthquake, Xinhua reported.

The freight train was carrying 13 tankers full of gasoline and was still burning Tuesday, when the first official confirmation of the accident came. Xinhua said there were fears the burning oil tanks, which had been buried by the rocks, could explode. More than 900 local residents were evacuated, it said.

In Chengdu, it crashed telephone networks and hours later left parts of the city of 10 million in darkness.

"We can't get to sleep. We're afraid of the earthquake. We're afraid of all the shaking," said 52-year-old factory worker Huang Ju, who took her ailing, elderly mother out of the Jinjiang District People's Hospital. Outside, Huang sat in a wheelchair wrapped in blankets while her mother, who was ill, slept in a hospital bed next to her.