Eleven dead, twelve missing, five hundred displaced and incalculable environmental damage. This is the provisional toll of the incident in which two dams collapsed at an iron mine owned by mining company Samarco, in south-east Brazil.

On 5 November, the village of Bento Rodrigues in Mariana, a town in the region of Minas Gerais, was engulfed by a wall of mud, slime, residue and toxic waste following the collapse of two dams built to contain wastewater.

Brazilian president Dilma Rousseff compared the incident to the environmental disaster in the Gulf of Mexico, caused by the British Petroleum oil platform.

More than 250,000 people are currently without drinking water, while the watercourses have taken on an alarming orange colour.

The collapse of the dams caused the spillage of more than fifty million cubic metres of sludge and liquid residue from mining operations, containing highly toxic substances such as mercury. Mining company Samarco agreed to pay 260 million dollars for the rupture of the two dams.

The company, owned by industry giants Vale and Bhp Billiton, repeatedly denied the toxicity of the mud and pledged to "make every possible effort to prioritise the needs of the people who were in the incident area," according to a statement released by Bhp Billiton.

"It has already been established that numerous wild animals have been killed by the mud," said Klemens Laschesfki, professor of geosciences at the University of Minas Gerais. "To say that the mud is not a health risk is an oversimplification."

The Brazilian authorities, however, consider the sum insufficient to cover the enormous damage to the environment and the population. "This is only a first instalment," said state prosecutor Carlos Eduardo Ferreira Pinto.

The causes and environmental consequences of the incident are not yet clear. According to scientists, the sludge, which may contain chemicals used to reduce impurities in iron, could alter the course of streams, reduce oxygen levels in the water and diminish the fertility of agricultural land.

The disaster is merely the latest blow to the Rio Doce river, one of the main links between the state of Minas Gerais and the Atlantic Ocean. The area, which passes through dense rainforest, has been subject to intensive mining — above all for gold and iron — since Portuguese colonisation.

Biologists now fear that the toxic substances released into the river could contaminate the coastline as well. The mouth of the Rio Doce is a nesting ground for sea turtles, creatures that are endangered and particularly sensitive to chemical changes in the water.

All animal species in the area, both terrestrial and aquatic, are dying from asphyxiation. To protect the fish fauna, Operation Noah's Ark has been launched, involving specialist fishermen and environmental associations to prevent the extinction of the species that inhabit the watercourse.