Lax regulations and chronic short staffing made the devastating collapse of a dam in southeastern Brazil all but destined to happen, experts and legislators have claimed.

The failure of the dam holding back iron ore mining waste unleashed an avalanche of mud that buried buildings and contaminated water downstream.

At least 115 people died in the collapse on 25 January, and another 248 people remain missing.

One of the cruelest aspects of the tragedy in Brumadinho is that it has happened before: in 2015, mining dams burst in nearby Mariana in what is considered Brazil's worst environmental disaster.

In the three years since the Mariana rupture killed 19 people, the regulation of the industry has reduced, not increased, in Minas Gerais state.

"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.

Problems that existed when the dams in Mariana burst have persisted, like dramatic short-staffing, while a new law has reduced the say of environmental groups in the project licensing process.

Environmental groups accused the previous Congress and president of rolling back significant protections, and many expect further weakening under president Jair Bolsonaro, who has said environmental regulation hamstrings several industries, including mining.

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

But the politics that contributed to the collapses in Minas Gerais are much more local. For centuries, the mineral-rich state has revolved around the mining industry - its name, given by Portuguese colonisers, translates to "general mines".

"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 CEO of Vale SA, which owned and operated the Brumadinho mining complex, acknowledges their regulatory measures fell short.

"Apparently to work under the (current) rules has not worked," Flavio Schvartsman said during a press conference several hours after the dam breach.

Officials have said they don't yet know why the dam collapsed.

Arrest warrants have been issued for five people responsible for safety assessments of the dam, including three Vale employees.

The Mariana collapse unleashed nearly 80 million cubic yards (60 million cubic metres) of mining waste into rivers and eventually the Atlantic Ocean.

While its environmental impact is considered the worst in Brazilian history, Brumadinho has already far surpassed its death toll.

In the wake of the Mariana tragedy, Minas Gerais was already struggling to implement what regulation it had: a 2016 audit found the state had only 20 per cent of the staff needed at the agency charged with regulating mines.

Mothers of babies afflicted by Zika fight poverty in Brazil Show all 16 1 /16 Mothers of babies afflicted by Zika fight poverty in Brazil Mothers of babies afflicted by Zika fight poverty in Brazil Gleyse Kelly da Silva embraces her daughter Maria Giovanna, who has microcephaly, in 2016. She has help from her husband and mother in caring for "Gigi". But the burden is still great, and she was forced to leave her job as a toll attendant Reuters Mothers of babies afflicted by Zika fight poverty in Brazil "She does not sit alone, she does not roll, she does not do anything alone," Gleyse said. Gigi needs an orthopedist, but there are not enough to go around, and she's perpetually on waiting lists Reuters Mothers of babies afflicted by Zika fight poverty in Brazil Gleyse holds her now two-year-old daughter Maria Giovanna, at their house in Recife. She struggles with navigating her daughter's wheelchair on public transportation. Few buses have working lifts, and some drivers have refused to help her. Such struggles prompted Gleyse to help create the Union of Mothers of Angels, which provides advice and logistical support for mothers of children with microcephaly. The group now serves more than 250 families in Pernambuco Reuters Mothers of babies afflicted by Zika fight poverty in Brazil A few years ago Jackeline Vieira de Souza fought to overcome a very rare complication from an earlier pregnancy, and then survived cancer. "My dream was to be a mother again," she says. In 2015, she got her wish. But during her pregnancy, she learned that her son had microcephaly. "When he was born, I fell in love with him because I knew he would be a good thing in my life, even with the difficulties I would have to face." In this picture Jackeline uses a green bottle to stimulate her then four-month-old son Daniel Reuters Mothers of babies afflicted by Zika fight poverty in Brazil Jackeline stands by as Daniel, who is now two years old, during an evaluation session with a physiotherapist at the Association of Parents and Friends of the Exceptional in Recife Reuters Mothers of babies afflicted by Zika fight poverty in Brazil Jackeline holds up Daniel, then just four months old. Daniel's father separated from Jackeline shortly after learning that his son had microcephaly. He pays a small amount of family support every month, in addition to a monthly check that Jackeline gets from the government Reuters Mothers of babies afflicted by Zika fight poverty in Brazil Daniel with his brother at their house. It takes several hours to travel by bus between their home in Olinda and Recife, where Daniel goes for treatments. Lately, those trips are somewhat less frequent, and Jackeline believes Daniel's health is more stable. She has no illusions that her son will ever walk, eat on his own or live a normal life. Yet in many ways she is grateful for her "miracle" baby, who she says makes her feel "happy and more accomplished." Reuters Mothers of babies afflicted by Zika fight poverty in Brazil Rosana Vieira Alves and her then five-month-old daughter Luana Vieira, who was born with microcephaly, in the sea of Porto de Galinhas. She has three daughters. "It's hard to manage the girls. Some of them are jealous, but Luana needs more care. In time, they'll understand." Reuters Mothers of babies afflicted by Zika fight poverty in Brazil Rosana holds up Luana at their house in 2016. She does not have any family support and is overwhelmed by the cost of housing and Luana's medicines. She counts it a victory that she has managed to get a wheelchair for Luana, and worries about the four surgeries her daughter needs to correct problems with her eyes, her gut and the position of her hips and feet Reuters Mothers of babies afflicted by Zika fight poverty in Brazil Rosana, 28, washes her now two-year-old daughter Luana. The demands have taken Rosana to some dark places, and she confesses that she has considered suicide. But she still dreams of a better future, and hopes to get a degree in accounting or civil engineering Reuters Mothers of babies afflicted by Zika fight poverty in Brazil Luana reacts to stimulus during an evaluation session with a physiotherapist at the Altino Ventura rehabilitation center in Recife Reuters Mothers of babies afflicted by Zika fight poverty in Brazil Rosana carries Luana (then four months old), while taking her daughters Laiane Sophia (left) and Vitoria Evillen to their school Reuters Mothers of babies afflicted by Zika fight poverty in Brazil Gabriela Alves de Azevedo, holds her then four-month-old daughter Ana Sophia, who was born with microcephaly, at their house in 2016. Gabriela had planned to finish high school and study physical therapy. Now, she spends her days caring for her child Reuters Mothers of babies afflicted by Zika fight poverty in Brazil Ana Sophia, now three-years-old, being held by Gabriela. Her husband left shortly after the birth. He could not accept their child's condition, Gabriela says, and does not pay child support Reuters Mothers of babies afflicted by Zika fight poverty in Brazil Gabriela bathing her Ana Sophia, in 2016. After he husband left she said: "I went into depression and my family helped me. If it was not for them, I would have gone crazy." Reuters Mothers of babies afflicted by Zika fight poverty in Brazil Silvina da Silva poses with her two-year-old granddaughter Ana Sophia Reuters

Environmentalists say mining regulation has got even weaker since.

In 2015, the state approved a new process for licensing mining projects. It shifted responsibility from a board that included several environmental organisations to the state environmental secretary, who created a new board with a majority of participants favourable to mining industry interests.

Then governor Fernando Pimentel argued the bill would reduce bureaucracy.

But 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".