SAO PAULO - A massive, deadly river of pale brown mud released by the collapse of a mining company dam threatens to cause an environmental disaster for Brazil, potentially snatching away livelihoods and driving the spread of disease, activists warned Sunday.

Mining giant Vale said the thick, slow-moving mud that is spreading down the Paraopeba River from Friday's dam collapse in southeastern Brazil is not toxic. But environmental organizations said the torrent of iron ore mine waste contains high levels of iron oxide that have the potential to cause irreversible damage.

Accidents on this scale trigger a domino effect, said Malu Ribeiro, a project co-ordinator at SOS Mata Atlantica, a non-profit organization that has been monitoring water quality since a similar disaster in the area in 2015.

"The entire ecosystem is affected," she said, bringing economic hardship for local communities and, for example, a proliferation of disease-bearing insects.

"Even if it was just sand, the volume is gigantic," said Carlos Rittl, a director at the Observatorio do Clima, a network of 43 nonprofits in Brazil. "There is a very fine residue (of iron oxide) that will be deposited on the bed of the river."

That means each time it rains heavily in the future, the iron ore deposit will be churned back up to the surface and contaminate the river again, experts say.

Officials at the Brazilian Environment Ministry could not immediately be reached for comment at the weekend.

In what is regarded as the worst environmental disaster in Brazilian history, a dam jointly operated by Vale and BHP Billiton collapsed just over three years ago in the same state of Minas Gerais, killing 19 people. The accident at the Mariana mining site also drove hundreds of people from their homes, left 250,000 people without drinking water and killed thousands of fish.

Vale insisted that the latest accident, near the city of Brumadinho, represented less of an ecological threat, though 37 people were reported dead as of Sunday.

"The damage from the environmental point of view is much lower than (Mariana's)," Vale CEO Fabio Schvartsman said, though he noted, "the human tragedy must be greater."

At the moment, environmentalists predict the impact of the latest dam collapse will be felt up to 300 kilometres (160 miles) from the mining site. That is far less than in 2015, when contamination was detected 670 kilometres (416 miles) away.

However, environmental organizations are anxiously watching to see whether a hydroelectric dam downstream from Brumadinho will be able to withstand the surge of mud coming down the River Paraopeba.

The two dam breaks have put Vale under fire from several directions.

Brazilian police are investigating the company for alleged corruption. Vale has also been accused of human rights abuses and of failing to comply with environmental regulations. It has paid fines in some cases and settled with authorities in others.

News from © The Associated Press, 2019