Geneva - Environment experts are monitoring closely 18 lakes that have formed following the earthquake in China, a UN spokesman said Tuesday.

They had been created by debris blocking the rivers the Office for the Coordination of Humanitarian Affairs (OCHA) told journalists in Geneva.

"These lakes could create a potential danger for the populations below if the rivers burst through once more," warned OCHA spokeswoman Elisabeth Byrs.

The threat was even greater with further aftershocks being forecast in the region.

Experts from the UN Environment Programme (UNEP) were also continuing to monitor two facilities in Shifang city which were still leaking sulphuric acid and ammonia.

The death toll has now risen to 40,000 in the earthquake that struck Sichuan Province on May 12.

OCHA said the biggest need was for tents with an estimated 5.7 million people evacuated as of May 16.

The children's agency, UNICEF, said they were providing a 1,000 tents. The Chinese authorities had asked them to send experts to work with children suffering from post-traumatic stress. A team was to spend five days in three towns.

More than 33,000 hectares of farmland had been flooded damaging wheat and vegetable crops in the 13 worst-hit cities and counties, according to information from the Ministry of Agriculture.

According to the latest UN figures 17 million dollars has been received in funding with a further 76.8 million in pledges from more than 20 donors. (dpa)