BRUMADINHO, Brazil — Two days after a torrent of mud pouring from a ruptured mining dam left at least 58 dead and 305 missing in the Brazilian town of Brumadinho, residents had to evacuate Sunday as a second dam threatened to collapse, sparking panic and outrage at what residents called a lack of accountability for Brazil’s powerful mining industry.
Sirens sounded before dawn, set off by heavy rains and dangerously high water levels at a dam at an iron ore complex owned by the Brazilian mining giant Vale S.A. Rescue workers looking for survivors from Friday’s disaster turned instead to evacuating residents to higher ground.
By the end of the day, residents were allowed to return to their homes. But for many Brazilians, this latest warning was further evidence that the system regulating the mining industry is broken, risking people’s lives and endangering the environment.
Still, few expect the rules to tighten under Brazil’s new president, Jair Bolsonaro, who promised during his campaign that he would restrict fines and ease regulations on mining and other industries that exploit natural resources.
There are more than 400 mining dams like the one that broke in Brumadinho in the state of Minas Gerais, the hub of Brazil’s mining industry. Three years ago, another such mining dam burst in the city of Mariana, 75 miles away, killing 19 people and unleashing one of the worst environmental disasters in Brazilian history. That dam was jointly owned by Vale and the Anglo-Australian mining company BHP.
Some of the dams have been deemed “unstable” but have continued operating for years, said Bruno Milanez, a professor of industrial engineering at the Federal University of Juiz de Fora. What is frightening, he said, is that the dams that broke — in Mariana and Brumadinho — were certified as “stable.”
In Brazil, independent auditors verify the safety of dams through regular inspections and analysis of written records. The problem, according to experts like Mr. Milanez and Luiz Jardim, a geography professor at the State University of Rio de Janeiro, is that the mining companies choose and contract with the auditors and provide all of the documentation that they analyze.
And that has not changed in the three years since the Mariana disaster, Mr. Jardim said. If anything, the regulatory framework in the state has become looser, as a drop in international commodities prices has prompted mining companies to cut costs, in some cases leading them to fill dams beyond capacity, reduce safety budgets and fail to put emergency systems in place, experts said.
“These are not exceptional events. Dams rupture. More will come,” Mr. Jardim said. “Either the monitoring system is flawed, or companies have figured out how to work around it.”
Vale’s chief executive, Fabio Schvartsman, said the cause of Friday’s breach was still being investigated. The Brumadinho dam has been inactive for three years and had been certified as stable as recently as this past December.
But a representative from Ibama, the federal environmental protection agency, warned at the time that the Brumadinho dams were not risk free.
“Any negligence on the part of those conducting risk management, and they rupture,” the representative said, according to notes of a December state council meeting on mining regulations that were sent to The New York Times.
At the meeting, council members voted on Vale’s request for a permit to expand operations in the mining compound that included the Brumadinho dam. Maria Teresa Corujo, an activist, was the only member to vote against it.
“I feel a mixture of pain, disgust, hatred and indignation,” she said about the approval, adding that the mining industry in the state of Minas Gerais “dominates all of the levels of power, it co-opts and threatens.”
One of the few concrete changes made after the Mariana disaster in 2015 was a requirement that mining companies install alarms in communities at risk from dam breaks.
Although the sirens blared ahead of the evacuation on Sunday, residents of Brumadinho said there was no warning ahead of the lethal torrent on Friday.
“They told us that if anything ever happened, an alarm would go off to give us time to get everything out,” said Dari Pereira, 39, a machine operator who escaped with his family seconds before a river of sludge swept over his house Friday.
There was no time to take clothes, the car or even pets, Mr. Pereira said. He heard a strange crackling sound, then the scream of his mother-in-law next door, saying the dam had broken. He ran, taking his children.
“Seconds after we left, I saw a wave drag away everything, the house, everything,” he said.
On Sunday, holed up in his sister’s house, he was woken up by sirens warning of a new threat.
“I got so scared,” he said. “I thought, not again, my God!”
Again the family ran out with just the clothes they were wearing, he said as he sat in a local health clinic with a small backpack of donated clothes and no clear idea of what to do next.
As they tried to make sense of what had been lost, many residents wondered why they hadn’t been warned about the risks.
Ademir Caricato, a community leader in the Parque da Cachoeira neighborhood, where roughly 40 houses were destroyed and at least one person was missing, said that Vale officials had told residents last year that the dam posed little danger.
“We would be the first to die,” he remembered one official saying, pointing out that the mine’s administrative offices were right below the dam.
Brazil’s attorney general, Raquel Dodge, announced a task force to investigate the cause of the Brumadinho disaster, and judges ordered Vale to set aside 11 billion reais, about $2.9 billion, to pay damages caused by the dam collapse.
But experts said they were skeptical that much would improve under the new far-right president, Mr. Bolsonaro, who campaigned on a pro-business platform openly hostile to environmental regulations. He promised to open up protected lands to mining and to eliminate the “industry” of environmental fines.
After surveying the disaster zone, both he and his environment minister, Ricardo Salles, said mining dams needed stricter regulation. But when Mr. Salles was the environment chief for the adjacent state of São Paulo, he tried, unsuccessfully, to make it easier for mining companies to get safety and environmental impact certificates.
After the Mariana disaster, Vale and BHP committed $780 million to create a fund for reparations and repairs, and settled a lawsuit worth much more with Brazilian federal and state prosecutors. But critics say the lack of personal accountability — including jail time — for those responsible has fueled the sense of impunity.
“Nobody has been held personally responsible. All of the managers and directors have moved on and are living normal lives,” Mr. Milanez said. “The chances of Brumadinho ending up the same way are very big.”