A dam holding waste water from an iron ore mine burst in the Brazilian state of Minas Gerais, devastating a nearby town with mudslides.
The mine is owned by Vale and BHP Billiton, who said in a statement that it had not yet determined why the dam burst or the extent of the disaster.
Civil defence authorities in Mariana said they were evacuating about 600 people to higher ground.
They could not immediately confirm the number of casualties... but local media said at least a dozen were feared dead.