China says nearly 400 dams and reservoirs near the epicenter of Monday's deadly earthquake were damaged, triggering new worries as Chinese officials warned Thursday, that the death toll could top 50,000.

Chinese paramilitary police wears mask during rescue operation at collapsed elementary school in Yingxiu, 15 May 2008

The military is in a race against time to rescue tens of thousands believed buried beneath the rubble from Monday's quake. Officials in southwestern Sichuan province say the known death toll has risen to more than 19,500.

The official Xinhua news agency says troops have been sent to repair cracks in the Zipingpu Dam in Sichuan.  China's water minister says there are major safety issues with dams, reservoirs, and hydropower stations in the earthquake zone.

The Chinese military has sent 130,000 troops to Sichuan and deployed 101 more helicopters to airlift victims and drop emergency supplies to quake survivors. 

Xinhua says 44 counties and districts in Sichuan were severely hit and the strains from tens of thousands left homeless are growing. The International Federation of Red Cross and Red Crescent societies has issued an emergency appeal for medical help, food, water and tents.

Landslides are still blocking efforts to reach 20,000 people in three towns near Wenchuan County where the quake originated. 

The Chinese government has also made a rare public appeal for donations of equipment to help with the rescue effort, such as hammers and shovels. Some rescuers have been digging through mountains of rubble with nothing but their hands.

Thursday, a professional emergency relief team from Japan left for China's earthquake-hit areas. The 30 member team will arrive in Sichuan's provincial capital, Chengdu, Friday and appears to be the first foreign rescue team to be allowed to help out on the ground.  

China's government has spent more than $150 million for disaster relief efforts, while public donations have reached more than $192 million in cash and goods for the recovery efforts. 

Some information for this report was provided by AFP, and Reuters.