By Agence France-Presse
Seven bodies were recovered Friday hours after the disaster, which saw a torrent of mud break through the disused dam at the iron-ore mine close to the city of Belo Horizonte, in the state of Minas Gerias, around 1:00 pm.
By early Saturday the official death toll had risen to nine, with "nearly 300 people missing," the local firefighters said, doubling the number of people presumed missing from the previous toll.
Up to 150 of those missing worked in the company's administrative offices which were closest to the dam break, the firefighters said.
The mine is owned by Vale, a Brazilian mining giant that was involved in a previous 2015 mine collapse in the same state that claimed 19 lives and is regarded as the country's worst-ever environmental disaster.
Vale shares plummeted on the new accident, losing eight percent in New York trading.
Romeu Zema, the governor of Minas Gerais, told reporters that, while all was being done to find survivors, "from now, the odds are minimal and it is most likely we will recover only bodies."
His regional administration said 427 people had been working at the Vale mine at the time of the dam collapse, and 279 were recovered alive. The others were listed as missing.
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The massive, muddy flow from the collapse barreled towards the nearby town of Brumadinho, population 39,000, but did not hit it directly.
Instead, it carved its way across roads, vegetation and farmland, taking down a bridge, and damaging or destroying homes.
Television images showed people being pulled out of waist-high mud into rescue helicopters, dozens of which were in use by late Friday because of the cut-off land access.
Brazil's new government led by President Jair Bolsonaro reacted to its first big emergency since taking office early this month by launching disaster coordination between the defense, mining and environment ministries and authorities in the affected state of Minas Gerais.
Bolsonaro and his defense minister were scheduled to fly over the zone on Saturday. His environment minister raced to the area late Friday.
"Where are our relatives?" wailed Raquel Cristina, one of several people demanding information about their missing kin in the mud-hit area.
"My five-year-old nephew is asking me if his dad died. What do I tell him?" asked another, Olivia Rios.
Officials said they were working through the night, conscious of the precious hours ticking away.
Around 100 fire fighters were deployed, some using earth-moving machinery to dig down to engulfed dwellings.
Would-be rescue volunteers were warned away because of the slippery, perilous piles of mud. Media were urged not to use drones to avoid collisions with the helicopters.
Vale CEO Fabio Schvartsman called the incident a "human tragedy" and was resigned to more deaths being confirmed at his company's mine.
"We're talking about probably a large number of victims -- we don't know how many but we know it will be a high number," he told a media conference in Rio de Janeiro.
Schvartsman, who had his two-year term renewed last month by Vale's board, said it was an "inactive dam" that was in the process of being decommissioned that burst apart "very violently, very suddenly."
Its contents -- tailings, or mining byproducts mixed with water -- cascaded into another dam, which overflowed, he said.
The disaster recalled trauma from the 2015 dam break near Mariana, in Minas Gerais. That accident released millions of tons of toxic iron waste along hundreds of kilometers (miles). Vale was joint operator of that dam, along with the Anglo-Australian group BHP.
The Brazil office of Greenpeace, the environmental activist group, said Friday's dam break was "a sad consequence of the lessons not learned by the Brazilian government and the mining companies."
It said the incidents "are not accidents but environmental crimes that must be investigated, punished and repaired."