Another dam operated by Brazilian miner Vale is at risk just miles from where 300 people are thought to have been killed when its Brumadinho dam collapsed in January.
A dam at the Gongo Soco mine in the State of Minas Gerais could burst within days, causing Vale to alert authorities in the region.
Nearly 460 people were evacuated from the area on 8 February, two weeks after the Brumadinho disaster, and the mine was put under round-the-clock monitoring.
“The rupture may happen between 19 May and 25 May, which could cause liquefaction of the south dam,” a document published by prosecutors said.
The dam at Gongo Soco, which has been inactive since 2016, holds around 6m cubic metres of waste from mining – so-called tailings.
Shares dropped 3.2 per cent yesterday, with markets yet to open this morning.
More than 300 people are either dead or missing after a dam burst in January near the city of Brumadinho.
The event, which pushed up global iron ore prices, has led to a clampdown in Brazil on mining waste dams.
Miners are now having to phase out their use of the dams over the coming years.