Transcript for Nearly 300 people feared dead after Brazilian dam collapses

Tara, thank you. Another big story we're following in Brazil, the catastrophic dam collapse. Workers on a lunch break when that dam gave way, unleashing a deadly sea of mud. Hundreds still missing. The death toll expected to soar. ABC's erielle reshef with the latest. Reporter: Harrowing images of helicopters swooping in. Rescue crews pulling sludge-soaked victims to safety. Tonight, the desperate search for 300 people feared washed away. At least 40 confirmed dead, this number expected to sharply climb. The mining CEO calling it a human tragedy. We don't know how many victims there are, he say. The vale dam rupturing Friday in the mining-heavy state of minas gerais Friday sending rushing red water tearing through the company's mine offices and a busy cafeteria during lunchtime. The CEO saying more than 250 employees are unaccounted for. The same area still recovering from a large dam collapse in 2015 that killed 19, the worst environmental disaster in Brazil's history. And tonight, that river of mining waste is raising widespread fears of contamination. Tom, those daring rescues you just saw there have led in part in rescuing 40 people and those rescue operations are continuing tonight. All right, erielle, thank you. Back here at home, the brutal cold. You can feel it on lake superior

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