(AP) -- There was no stopping the avalanche of toxic red sludge when it rammed into Kati Holtzer's home: It smashed through the main door and trapped the woman and her 3-year-old boy in a churning sea of acrid waste.
She saved her son by placing him on a sofa that was floating in the muck. She called her husband Balazs, who was working in Austria, to say goodbye.
"We're going to die," she told him, chest-deep in sludge.
After the terror came the pain: Holtzer and her two rescuers are among the 120 people suffering from biting chemical burns after Monday's torrent. Her fox terrier Mazli - "Luck" in Hungarian - lies dead in the yard, still chained to a stake.
The ecological catastrophe that is threatening the Danube River - one of Europe's main waterways - is leaving a trail of shattered lives in its wake, even as officials scrambled Wednesday to stem the flow.
Hundreds of people were evacuated Monday after a gigantic sludge reservoir burst its banks at a metals plant in Ajka, a town 100 miles (160 kilometers) southwest of Budapest, the capital.
The torrent inundated homes, swept cars off roads and damaged bridges, disgorging an estimated 1 million cubic meters (35.3 million cubic feet) of toxic waste onto several nearby towns. At least four people have been killed and three are still missing.
Emergency workers and construction crews in hazmat gear swept through the hardest-hit Hungarian towns on Wednesday, straining to clear roads and homes coated by thick red sludge and caustic muddy water.
In Brussels, the European Union said it feared the toxic flood could turn into an ecological disaster for half a dozen European nations - those downriver from Hungary along the mighty Danube - and said it stood ready to offer help.
"This is a serious environmental problem," EU spokesman Joe Hennon told The Associated Press on Wednesday. "We are concerned, not just for the environment in Hungary, but this could potentially cross borders."
In Kolontar, the town nearest to the plant, a military construction crew worked to assemble a pontoon bridge Wednesday across a toxic stream so residents could briefly return to their homes and rescue belongings.
For two days, workers in full hazmat gear with respirators have contrasted sharply with locals, who have salvaged possessions with little more than rubber gloves as protection. Women with pants coated in the red mud have been seen clearing the muck away from their homes with snow shovels.
Red sludge is a byproduct of the refining of bauxite into alumina, the basic material for manufacturing aluminum. It contains heavy metals and is toxic if ingested. Treated sludge is often stored in ponds where the water eventually evaporates, leaving behind a dried red clay-like soil.
It was still not known Wednesday why part of the reservoir failed, unleashing such an unstoppable torrent. Hungarian Prime Minister Viktor Orban says authorities were caught off guard by the disaster since the plant and reservoir had been inspected only two weeks earlier and no irregularities had been found.
Kolontar mayor Karoly Tily said Wednesday he cannot give a "reassuring answer" to residents, who fear a repeat of Monday's calamity.
Hungarian environmentalist Gergely Simon said the sludge had been accumulating in this reservoir for decades and was extremely alkaline, which caused it to burn the skin of dozens of residents.
Emergency workers, meanwhile, were pouring 1,000 tons of plaster into the Marcal River to try to bind the sludge and keep it from flowing into the Danube, 45 miles (72 kilometers) away.
At 1,775 miles (2,850 kilometers) long, the Danube is Europe's second largest river and holds one of the continent's greatest treasuries of wildlife. South of Hungary, the Danube flows through Croatia, Serbia, Romania, Bulgaria, Ukraine and Moldova before emptying into the Black Sea.
The river has already been the focus of a multibillion dollar 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.
MAL Rt., the Hungarian Aluminum Production and Trade Company that owns the Ajkai plant, has insisted the red sludge is not considered hazardous waste according to EU standards. The company has also rejected criticism that it should have taken more precautions to shore up the reservoir, a huge structure more than 1,000 feet (300 meters) long and 500 yards (450 meters) wide.
Hennon, the EU spokesman, said the company did have a license to operate and added "we have nothing to indicate there was anything wrong with it."
Hennon said the EU has funds available to deal with natural disasters, but it first needs to assess whether the spill was a natural disaster or a man-made calamity, which will determine how much liability the company faces.
"There are quite a few open questions and it's a bit too early to say exactly what the situation will be," Hennon said.
The current European safety standards came into effect in 2007 but the EU will reassess its law to see anything needs to be changed, he said.
"We are going to look very carefully at the outcome of what caused this, what the effects are, and then we will assess whether we do need to look again at the legislation," Hennon said.
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