A dam collapsed at an iron ore mine owned by Vale SA in Brazil, leaving some 200 people missing, the fire brigade in Belo Horizonte, the capital of the state of Minas Gerais, said in a statement.
At least 50 people died as a result of the disaster, local newspaper Hoje em Dia reported, quoting Avimar de Melo, the mayor of Brumadinho.
A fireman told Reuters that some 100 Vale SA employees among the missing were at lunch in the area at time of the disaster.
Vale SA, a Brazilian multinational corporation, is one of the largest logistics operators in Brazil and also the largest producer of iron ore and nickel in the world.
The incident comes four years after the collapse of another iron ore tailings dam in Brazil, which was owned by Vale SA and BHP Billiton. That collapse killed at least 17 people and is described as the worst environmental disaster in Brazil's history.