Map of the earthquake's reach.
The earthquake was felt as far away as Laos and Vietnam.
Chinese troops have repaired a dam cracked in this week's earthquake, but officials remain concerned about the damage to reservoirs in the devastated Sichuan province.
China's top economic planning body said the magnitude 7.9 quake damaged 391 mostly small dams when it struck Monday. He Biao, the director of the Aba Disaster Relief headquarters in northern Sichuan province, said officials are concerned about dams close to the epicenter.
"Currently, the most dangerous problems are several reservoirs near Wenchuan," the relief director said, according to a transcript on the CCTV Web site. "There are already serious problems with the Tulong Reservoir on the Min River. It may collapse. If that happens, it would affect several power plants below and be extremely dangerous."
The Chinese government sent about 2,000 soldiers to make the repairs to Zipingku Dam on Wednesday, fearing that it might collapse and flood the hard-hit city of Dujiangyan, according to a statement on the Sichuan government Web site. Still, the reservoir behind the dam was emptied to relieve pressure on the structure, the state-sponsored Chinese business news magazine Caijing reported.
As the government worked to repair dangerous structures, relief workers spent Wednesday looking for survivors and distributing supplies that were air-dropped into the stricken area. Their work was hampered by the huge scale of the devastation, where landslides and collapsed buildings made many roads impassible.
Help arrived by helicopter and on foot in some of the hardest-to-reach areas, where many people were still trapped under debris.
The official death toll rose Wednesday to 14,866, the official Xinhua News Agency reported. It was not immediately clear if that number included 7,700 reported dead in the city of Yingxiu. Xinhua quoted government officials as saying rescuers who hiked into the city found only 2,300 survivors in the town of about 10,000, and 1,000 were badly hurt.
Twelve Americans were found safe near the epicenter of the quake. A spokeswoman for the World Wildlife Fund said the 12 were near the world famous panda preserve in Wolong, whose pandas were reported safe Tuesday.