The owner of the mine said it had not determined why the dam burst or the extent of the disaster at its Germano mine near the town of Mariana, Reuters reported.
Between 15 and 16 people died and 45 others were missing, Brazilian G1 news service reported, citing the local union.
Video footage on the G1 website showed houses of a village destroyed by muddy tailings waters that surged down valleys in the hilly region of the mines.
The mine is a 50-50 joint venture between the world's largest iron miner and the largest mining company.
Tailings is the term for the sand-like waste rock that has been left behind from the process of grinding up and separating minerals from ore. A tailings dam contains the pond where tailings are deposited.
There are currently about 3,500 tailings dams worldwide.