While business reporting zooms in on the financial implications of last week's deadly dam burst in Brazil—a toxic breach being called the "largest-ever spill of its kind"—survivors and rescuers continue to tally up the human and ecological costs and search for those who are still missing.

There are currently 28 people missing and three have been confirmed dead.

Reuters reports Monday that mud and wastewater from the burst dams is complicating search and rescue efforts while raising health and environmental concerns. Four days after the disaster, mud and mining waste is still running past the well-populated banks of the Rio Doce river, according to the news outlet, which adds:

Exhausted firefighters waded through waist-deep mud as thick as wet concrete among the tangled remains of Bento Rodrigues, a 600-person village that stood in the shadow of the broken dams in an area about a six-hour car ride north of Rio de Janeiro. [...] State health officials are checking the toxicity of the waters and warned residents who came in contact with the mud to throw out their clothing. Biologists warn that the environmental impact may be permanent, devastating local fisheries and farms.

Meanwhile, according to the Wall Street Journal, investors continued to dump shares in mining giant BHP Billiton Ltd. Monday while the company sought to pin the blame for Thursday's tailings dam collapse on its subsidiary, Samarco, which it owns jointly with another corporation. Samarco, BHP told the WSJ, was "responsible for the entirety" of the operations at the iron ore mine.

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The WSJ reports: "The cost to the companies, including for cleanup and rebuilding, could top US$1 billion, said Paul Young, a Sydney-based analyst at Deutsche Bank, who estimated the mine could be closed until about 2019."

As the WSJ noted on Sunday, large mining companies have experienced a rise in fatal accidents in 2015. On Saturday, the Estado de S. Paulo newspaper reported that a study commissioned by the state government in 2013 had warned that the very dams that burst last week could be vulnerable to collapse.

The Samarco mine is located in the so-called iron quadrangle, one of the most heavily mined regions in the world.

VICE News offered a view of the devastation from above: