Video footage has revealed the moment a dam collapsed in southeastern Brazil, leaving at least 115 dead and another 248 missing.

The film shows an avalanche of mud and waste sweeping across the iron ore mine before burying buildings and contaminating water downstream.

It was shown on Brazilian TV as experts claimed that weak safety controls and chronic short staffing meant the tragedy in Brumadinho was a “disaster waiting to happen”.

Environmental groups say industry regulations have reduced, rather than increased, since mining dams burst in nearby Mariana in 2015, killing nine people, destroying forests and contaminating nearby rivers.

Many expect the weakening of protections to continue under new president Jair Bolsonaro, who has claimed regulation is hampering several industries including mining.

Both Mariana and Brumadinho are in the mineral-rich state of Minais Gerais, which has revolved around the mining industry since the colonial era. Its name, given by Portuguse colonists, translates to “General Mines”.

Brazil dam collapse leaves town buried in waste Show all 7 1 /7 Brazil dam collapse leaves town buried in waste Brazil dam collapse leaves town buried in waste A building lays in ruins after a dam collapsed in eastern Brazil. AP Brazil dam collapse leaves town buried in waste A road near Brumadihno is blocked by waste. AP Brazil dam collapse leaves town buried in waste An aerial view of the burst dam in eastern Brazil. AFP/Getty Images Brazil dam collapse leaves town buried in waste The flow of waste spread from the dam to a nearby village. AP Brazil dam collapse leaves town buried in waste A firefighters' helicopter hovers as rescuers work in the search for victims AFP/Getty Images Brazil dam collapse leaves town buried in waste An aerial view shows flooding triggered by a dam collapse near Brumadinho. AP Brazil dam collapse leaves town buried in waste An aerial view after a dam collapsed near Brumadinho, Brazil. AP

“Minas Gerais has a centuries-long history of being lenient with the mining sector. It’s cultural,” Joao Vitor Xavier, a state deputy, said.

“The industry creates a discourse where they dangle jobs and economic growth in front of people, but they put profit over safety.”

The Brumadinho mining complex is owned by the multinational mining corporation Vale SA, which was also partly involved in the running of Samarco, the company responsible for the dams that collapsed in Mariana.

Vale’s CEO acknowledged their regulatory measures fell short. ”Apparently to work under the rules has not worked,” Flavio Schvartsman said during a press conference several hours after the dam breach.

Arrest warrants have been issued for five people responsible for safety assessments of the dam, including three Vale employees. However officials say they do not yet know why the dam collapsed.

Following the Mariana disaster in 2015, investigators discovered that Samarco had been warned about the possibility of a dam collapse.

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It unleashed nearly 80 million cubic yards (60 million cubic metres) of mining waste into rivers and eventually the Atlantic ocean.

The same year, the state approved a new process for licensing mining projects, supposely to reduce bureaucracy, which shifted responsibility from a board that included several environmental organisations to the state environmental secretary and a new board with a majority of participants favourable to mining industry interests.

Days before the law was approved, the Minas Association of Environmental Defence called it “one of the biggest setbacks in environmental regulation in the country.”

An audit the following year found the state had only 20 per cent of the staff needed at the agency charged with regulating mines.

But while the environmental impact of the Mariana disaster is considered the worst in Brazilian history, Brumadinho has already far surpassed its death toll.

“It felt like it was just a matter of time before something bigger would happen,” said Josiele Rosa Silva Tomas, the president of the Brumadinho residents’ association.