Emergency crews worked Friday to secure 15 sources of radiation buried in the rubble of China's devastating earthquake, the government said as it evacuated thousands of survivors downstream from rivers dammed by landslides.
Officials precariously balanced their efforts to clean up and rebuild with attempts to house, feed and treat the displaced and injured and search for survivors.
One senior official said China faces "a daunting challenge" to prevent environmental contamination from other sources.
There has been no leak of radioactive substances into the environment, Wu Xiaoqing, China's vice minister for environmental protection, told reporters in Beijing.
He said 50 sources of radiation were buried by debris from the massive earthquake in central China, 35 of which had been secured. The rest lay buried or located but unreachable under collapsed buildings. He gave no specifics about the radiation sources.
The number of unsecured sources was far higher than the two the government reported earlier this week. Foreign experts say the radioactive sources likely came from materials used in hospitals, factories or in research, not for weapons.
U.S. State Department spokesman Tom Casey told reporters that Washington was not aware of any threat to humans, "but, obviously, it is a concern."
He added that many of the locations were remote and the U.S. was relying for much of its information on the Chinese government.
Wu cautioned that a number of other "hidden" sources of pollution are likely to be encountered as workers begin digging into the rubble, which includes numerous factories and refineries.
The worst-hit areas in Sichuan province include many high-risk petrochemical and chemical companies, he said. Around three-fourths of the more than 100 chemical plants in the quake-hit area were forced to stop production as a result of damage, he said.
No environmental damage has so far been recorded, but as factories begin production, officials would need to vigilant to ensure chemical waste found of produced was properly disposed of, he said.
"We now face more daunting challenges in investigating and removing hidden troubles and carrying out environmental inspections as time passes by and factories gradually resume production," he said.
As the government continued to bring relief to the devastated areas of Sichuan, it was evacuating thousands downstream from rivers that were dammed by landslides.
With their waters pooling, the blocked rivers could breach the earthen barriers, a danger that would grow with coming rains or in aftershocks from the quake.
The confirmed death toll rose to 55,740 and another 24,960 remained missing 12 days after the quake, said the State Council, China's Cabinet.
The government was shifting focus to long-term reconstruction and away from the search for survivors and bodies among the wreckage.
Chinese banks were told Friday to forgive debts owed by survivors in an effort to revive the shattered economy, and the government warned it was cracking down on price-gouging by merchants in the disaster area.
The government also said it sent more fuel from China's strategic reservces to the quake-affected areas.
Beijing also ordered its richest provinces and cities to adopt areas that were hit hard by the quake and to start sending aid right away, especially tents and drinking water.
Vice Governor Li Chengyun said the province would aim to rebuild roads and cities within three years.
Back in the Sichuan provincial capital of Chengdu, a Dutch rescue and recovery team with sniffer dogs complained that soldiers prevented it several times from entering disaster areas, abandoning the search for survivors and bodies to focus on rebuilding.
"They have stopped searching and they want to clear things out," said Saad Attia of the group Signi, which arrived Saturday with Labrador retrievers and Belgian shepherds. "They are allowing no one in, not even the cadaver dogs."
Sichuan Vice Governor Li said the search has not been abandoned.
"We will not give up on trying to save people," Li said.
Six pandas were moved Friday from a damaged panda-breeding base in Wolong near the epicenter because of food shortages, the official Xinhua News Agency said. They were taken to another preserve in Sichuan, near a city called Ya'an.
Two pandas missing since the quake have still not been located.