Two helicopters carrying armed police who were to take part in the emergency remediation of a dangerous quake-formed lake in Sichuan Province were forced back to the airport by adverse weather on Saturday.

An armed police officer said low visibility caused by thick clouds at the Tangjiashan lake site made it impossible for the helicopters to land.

One helicopter carrying several armed police and experts had managed to land at the site earlier in the day.

The Tangjiashan "quake lake," which is in danger of bursting as water builds up in it, is one of the more than 30 such lakes in rivers blocked by landslides from the May 12 earthquake and thousands of aftershocks.

The lake is 3.2 km upstream from the Beichuan County seat, from which thousands of survivors have been evacuated.

As of Friday, the lake had collected about 100 million cubic meters of water and was in danger of overflowing, posing a serious threat to residents downstream.

Experts planned to dig sluice channels to reduce the water level in the lake.

(Xinhua News Agency May 25, 2008)