The jump in sand excavation is fueled by demand from Singapore's construction industry, which is searching for new sources after Indonesia and Cambodia banned exports.

Nguyen Van Be, director of the department of Natural Resources and the Environment in the province of An Giang, said illegal dredging in the Mekong Delta had caused landslides and altered the courses of rivers.

Be's colleague Tran Anh Thu said oil discharges from dredging barges were polluting river water, damaging the region's fish farms.

"We have strengthened inspections of this illegal activity, but it is difficult to stop," said Be. "When we go to check, people stop dredging, but when we go away, they start again."

According to the customs department in the Mekong Delta port of Can Tho, the volume of sand exported to Singapore from the area in the first half of 2009 topped 7mn tonnes, up from just 1.1mn tonnes last year. Total exports for 2009 are expected to top 10mn tonnes.

The surge has taken place even though the national government banned all sand exports last October.

The ban exempts all contracts signed before November 30, 2008. Can Tho customs official Nguyen Minh Thong said sand exporters were simply altering the dates on contracts to make it appear they had been signed before the deadline.

Thong said his department was not responsible for checking that the dates on contracts were correct.

Sand exporters have responded to a surge in the price of sand after Cambodia banned exports on May 18.

Construction industry sources said sand, which had sold for $1 cubic metre or less before the Cambodian ban, was now selling for $2.35 per cubic metre or more.

Vu Duc Hung, a water police official in Can Tho, said the local channels of the Mekong River were "filled" with sand-dredging barges.

Deutsche Presse Agentur - September 2, 2009