The disaster area is home to China's chief nuclear weapons research lab in Mianyang, as well as several secretive atomic sites, but no nuclear power stations.

Minister of Environmental Protection Zhou Shengxian convened an emergency meeting late on Monday, hours after the 7.9 magnitude tremor rocked the southwestern province of Sichuan, and activated the lowest tier of a four-stage system of ranking radiation leaks, the ministry said on its website.

President Hu Jintao flew to Mianyang on Friday, four days after the quake, which is thought to have killed more than 50,000 people, state television and the official Xinhua news agency reported, in an indication the risk was low.

Xinhua didn't say if Mr Hu had inquired about nuclear facilities there.

But nuclear scientists were evacuated from the area as a precaution, a source with knowledge of the evacuation said.

A Western expert with knowledge of the Mianyang lab had said it was unlikely it was at serious risk.

A Chinese Foreign Ministry spokesman said this week he had not heard of damage to nuclear facilities in the disaster area when asked at a regular news briefing.

More evacuation plans
The government is also drawing up evacuation plans amid concerns that dams in areas hit by the quake could collapse if rain there persists, state media reported on Friday.

The Ministry of Land and Natural Resources has ordered local governments in southwestern China to draw up plans to evacuate residents, the China Business News reported, amid forecasts of showers in the area.

The risk is particularly acute in devastated areas of Sichuan province such as Wenchuan and Beichuan counties near the earthquake epicentre, it said.

'Due to the serious disaster situation in Wenchuan, Beichuan and surrounding areas, the hidden dangers going forward are great,' it quoted ministry experts as saying.

The government warned on Thursday of 'dangerous situations' at more than 400 reservoirs in southwestern China following the quake, according to state media reports.

China's top economic planning agency said Friday it had allocated 53 million yuan (S$10.4 million) in emergency funds to assess and repair damaged dams and reservoirs, Xinhua news agency said. -- AFP