The Brazilian government has pledged to ease environmental licensing regulations just days after the deadliest mining disaster in decades prompted calls for tougher controls and stricter punishments for ecological crimes.

The torrent of mud and iron ore tailings that engulfed the community of Brumadinho on Friday continues to inflict a toll on residents, river systems and freshwater species.

Rescue teams had by Monday recovered 60 bodies near the site, which is operated by Vale, one of the world’s biggest mining companies, but hundreds of people are still missing. Many were eating lunch or resting in a hotel when the tailings dam collapsed and swept them away in a tide of orange sludge.

It is the second such calamity to strike a Vale facility in the state of Minas Gerais in less than four years. In 2015, 19 people were killed when a tailings dam burst at an iron ore mine in Mariana that the Brazilian company co-owned with the London-listed BHP Group.

The amount of slurry this time is 75% lower, at 13 million cubic metres, but now, as then, the ecological damage is spreading far beyond the immediate area and could potentially persist for many years with grave consequences for local communities, wildlife and the national economy.

Over the weekend, TV and social networks were filled with images of emergency workers in helicopters trying to pull people out of the mud. Now many posts have switched to the impact on fish, frogs and other freshwater species.

“Rio Paraopeba has started to die,” noted one grim tweet with a video clip of oxygen-deprived fish leaping out of the turbid water and flapping their last on the land.

The level of toxicity in the tailings is not yet clear, but iron oxide can choke river sand and poison the surrounding vegetation. It can also compact the soil, preventing new growth of plants on land. Three years after the previous disaster, water from the affected Doce River is still legally unfit for human consumption in 90% of monitoring stations.

A second and bigger impact is the amplification by previous manmade environmental problems. The torrent of water stirred up the heavy metals buried in the sediment on the bottom of the river. This is a huge problem in the state of Minas Gerais, which has a long history of poorly regulated resource extraction, according to the International Union for the Conservation of Nature (IUCN), which is working on a series of reports on the ecological impact of the previous tailings dam collapse in Mariana.

The immediate threat is to the 280km (174 miles) of Paraopeba River. Vale insists the problem will not spread to the São Francisco basin, but conservationists remain concerned. In this region, 64% of fish species are found nowhere else on Earth, according to the IUCN. Even before the contamination, 10% were already classified as vulnerable, including Simpsonichthys picturatus and Brycon orthotaenia. January is the end of the spawning season, which means the deluge affected fry and small fish in important species for fisheries, such as croakers, curimbatás and surubins.

Brazil has the most abundant water resources in the world, but they are tapped with often reckless abandon and inadequate regulation. Less than one in five of the country’s 24,092 dams come under the supervision of the 2010 dam safety law, 42 are unauthorised and 570 have no responsible operator, according to the Folha de São Paulo newspaper. With a mere 154 inspectors for such a vast country, only 3% of Brazil’s dams were inspected last year, it said.

The problems date back decades, but the risks look set to grow. The new administration of the president, Jair Bolsonaro, has neutered the environment ministry and pledged to ease the licensing system for new projects.

Despite the latest calamity, Augusto Heleno, the head of the national security office, insisted the fast-track approval process would go ahead. “Making the process more flexible means having very strict rules, but allowing certain works that depend on licensing to happen. It does not mean loosening environmental licensing. On the contrary, licensing has to be done well, but it can not be delayed without fair grounds,” he said.

Campaigners say this should now be unthinkable. “It would be offensive to victims of Mariana and Brumadinho if they fulfil that promise,” said Carlos Rittl, who heads the Climate Observatory umbrella group of environmental NGOs.

“This cannot be called an ‘accident’ under any circumstances,” said Malu Ribeiro, the founder of the NGO SOS Mata Atlantica. “Such environmental crimes should be punished with the legal rigour that society expects.”

Vale’s chief executive, Fabio Schvartsman, said in a television interview on Sunday that he did everything the law required. “I’m not a mining technician,” he said. “I followed the technicians’ advice and you see what happened. It didn’t work. We are 100% within all the standards, and that didn’t do it.”