2,000-mile wildlife bank

The International Commission for the Protection of the Danube, which manages the river and its tributaries, said the sludge spill could trigger long-term damaging effects for both wildlife and humans.

The Danube, at 1,775 miles long, is Europe's second largest river, behind the Volga, and holds one of the continent's greatest treasuries of wildlife. The river has already been the focus of a multi-billion-euro post-Communist cleanup, but high-risk industries such as Hungary's Ajkai Timfoldgyar alumina plant, where the disaster occurred, are still producing waste near some of its tributaries.

Philip Weller, the group's executive secretary, said the commission's early warning system was triggered by the spill, which means factories and towns along the Danube may have to shut down their water intake systems.

The Vienna-based commission was waiting for further details of the spill from Hungarian authorities, he said.