A toxic red sludge spill from an alumina plant in western Hungary has reached the Danube.
A spokesman for Hungarian disaster crews said there were no reports of fish dying in the Raba and Mosoni-Danube rivers which were hit by the spill earlier today, but all fish had died in the smaller Marcal river.
Clean-up crews are trying to dilute the chemicals to protect the major European waterway.
The toxic sludge has swept through local villages, killing four people and injuring 120. Three people are still reported missing.
Hungary declared a state of emergency in three counties on Tuesday after the sludge - waste from bauxite refining that has a strong caustic effect and heavy metal content - struck Kolontar, Devecser and other villages.
Prime Minister Viktor Orban visited Kolontar today and said there was no point in even removing the rubble from part of the village as it was impossible to live there again.
"It is difficult to find the words. Had this happened at night, everybody would be dead," Mr Orban told reporters. He reiterated that the disaster could not have been due to natural causes.
"This is an unprecedented ecological catastrophe in Hungary. Human error is more than likely. The wall (of the reservior) did not disintegrate in a minute. This should have been detected. We are fighting in order to stop the pollution before the Danube."
Hungarian branch director of the WWF environmental group Gabor Figeczky, who visited the scene along with experts, said the impact on the river Marcal was worse than expected and it was hoped the alkalinity would drop once it reached the Raba, a bigger river.
Mr Figeczky said that since the Danube was a much larger river, the alkalinity should dilute. "Based on our current estimates, it (pollution) will remain contained in Hungary, and we also trust that it will reach Budapest with acceptable pH values," he added.
Downstream from the disaster site, the Danube flows through or touches on Croatian, Serbian, Bulgarian, Romanian, Moldovan and Ukrainian territory en route to the Black Sea.
MAL Zrt, owner of the alumina plant and burst reservoir, said on Tuesday there had been no sign of the impending disaster, adding that the last inspection of the reservoir on Monday had shown nothing wrong.
The company said today that it would like to restart production at the as early as this weekend with a new sludge containment pond.
Lajos Tolnay, chairman of MAL, told business daily Vilaggazdasag that if the company were to stop operation, 3,000 jobs would be lost.
Disaster crews, military and local villagers were clearing away the rubble and searching for the three missing people. Many people had suffered from burns and eye irritations caused by lead and other corrosive elements in the mud.
The flood, estimated at about 700,000 cubic metres, swept cars off roads and damaged bridges and houses.
Agencies