RIO DE JANEIRO (REUTERS) - Mud from a dam that burst at an iron ore mine in Brazil earlier this month, killing 12 people and polluting an important river, is toxic, the United Nations' human rights agency said on Wednesday.
The statement contradicts claims by Samarco, the mine operator at the site of the rupture, that the water and mineral waste contained by the dam are not toxic.
Citing "new evidence," the UN's Office of the High Commissioner for Human Rights said in a statement the residue"contained high levels of toxic heavy metals and other toxic chemicals."
The agency did not say what studies were the basis for the evidence, nor who had conducted them.
The owners of Samarco, Brazil's Vale SA and Australia's BHP Billiton, did not have immediate comment on the UN statement.
Both companies have also said the mud is not dangerous.
Biologists have been shocked by the impact of the burst dam, which Brazil's government has called the country's worst-ever environmental disaster.
The mud has killed thousands of fish as it flows through the Rio Doce river, which connects the mineral-rich state of Minas Gerais with Espirito Santo on the Atlantic coast.
The 60 million cubic meters of mine waste, equivalent to 25,000 Olympic swimming pools, cut off drinking water for a quarter of a million people and the dense orange sediment has now reached the ocean.
The UN statement criticised the response of the companies and the Brazilian government as "insufficient."
It said "the government and companies should be doing everything within their power to prevent further harm."