EU warns spill could pose 'serious environmental problem' for 12 countries, as Hungarians told cleanup may take a year

Rivers and lakes in 12 European countries are in danger of being contaminated as toxic sludge from a factory in Hungary heads towards the Danube, EU officials said today.

"This is a serious environmental problem," said Joe Hennon, a spokesman for the EU. "We are concerned, not just for the environment in Hungary, but this could potentially cross borders."

Emergency workers have poured 1,000 tonnes of plaster into the Marcal river to try to bind the sludge that burst from a waste reservoir and keep it from flowing on to the Danube, 45 miles away.

At 1,770 miles (2,850km), the Danube is Europe's second longest river, and it is rich in wildlife. South of Hungary, it flows through Croatia, Serbia, Romania, Bulgaria, Ukraine and Moldova before reaching the Black Sea.

Hungary's environment minister, Zoltan Illes, said topsoil would have to be removed throughout the contaminated area, adding that the cleanup could cost tens of millions of pounds and take at least a year.

"The area is very big, there is very heavy contamination. Lots of human resources are needed, definitely machinery is needed," he told the BBC.

Hungary declared a state of emergency in three counties yesterday after a dam burst at an alumina plant in Ajka, releasing a torrent of toxic red sludge that swept through local villages. Four people were killed, three reported missing and 120 were injured.

Disaster crews were today expected to reopen the streets of Kolontar, the town nearest the plant, to allow residents to return for some of their belongings. The military put up a pontoon across a toxic stream so residents could reach the town, while bulldozers cleared away rubble.

"I'm waiting to finally be able to return to my house, but I don't think I'll ever move back here," an affected resident, Balazs Holczer, 35, told Reuters. "My wife and my son were trapped inside the house during the spill. She put him on top of a cabinet, and she was seriously burned from the waist down ... they are both in hospital, my son is still in a shock. He says he doesn't ever want to come back because he feels safe in the hospital."

Gyorgy Bakondi, the head of the national disaster unit, told Hungarian television that emergency workers were expected to close the break in the reservoir today. He said crews were also clearing the red sludge from the walls of houses as well as the streets.

"The third key thing is the protection of waters," he said. "This requires a very intensive intervention."

MAL Zrt, which owns the plant, has insisted that, according to EU standards, the sludge is not considered hazardous waste. The company has also rejected criticism that it should have taken more precautions to shore up the reservoir, which is more than 450 metres long and 300 metres across.

Environmental activists dismissed the claim that the sludge was not hazardous as ridiculous and accused the company of acting irresponsibly.

The Hungarian interior minister, Sandor Pinter, said of MAL Zrt's claim: "They should take a swim in it and then they'll see."

Viktor Orbán, the country's prime minister, acknowledged that authorities were caught off guard by the disaster. He added that the alumina plant and reservoir had been inspected two weeks earlier and no irregularities had been found.

Red sludge is a byproduct of the refining of bauxite into alumina, the basic material for manufacturing aluminium. It is common to store treated sludge in ponds where the water eventually evaporates, leaving behind a dried red clay-like soil.