The Brazilian government says it will sue mining company Samarco $5.2bn (£3.4bn) for the environmental damage caused after a waste water dam at an iron-ore mine collapsed.
At least 13 people died when the dam burst earlier this month in the south-eastern state of Minas Gerais
A village was destroyed and drinking water polluted over a wide area.
Environment Minister Izabella Teixeira said money was needed for environmental recovery and to compensate victims.
"There was a huge impact from an environmental point of view," she told reporters in the capital Brasilia.
"It is not a natural disaster, it is a disaster prompted by economic activity, but of a magnitude equivalent to those disasters created by forces of nature."
She said about 500km (310 miles) of the Rio Doce - one of Brazil's most important rivers - would have to be dredged in parts, vegetation replanted and fresh water springs cleared.
Samarco is owned by mining giants Vale, from Brazil, and Anglo-Australian company BHP Billiton.
On Thursday the UN said the dam burst had unleashed a flood of "toxic mud".
However, mining giant BHP said in a statement that the water in the dam - a by-product of iron ore extraction - did not pose any threat to humans.