Rescue officials said more bodies were being pulled out of the mud after the Brazil dam collapse.

Thirty-four people were confirmed dead and nearly 300 missing Saturday, with hopes fading of them being found alive, after a dam collapsed at a mine in southeast Brazil.

The disaster struck Friday at the Vale mine near the city of Belo Horizonte in Minas Gerais state, spewing millions of tons of muddy sludge across the facility and down towards farmland alongside the nearby town of Brumadinho.

Dozens of helicopters were used in the rescue operation Saturday because the released mud engulfed buildings, vehicles and roads with a deep, treacherous layer.

Rescue officials announced the death toll had more than tripled through the day as more and more bodies were pulled from the mud.

By the last count, nearly 300 people were missing, virtually all of them mine workers listed by Vale.

Among the more than 170 survivors rescued, 23 were hospitalized with injuries.

Brazilian President Jair Bolsonaro flew over the devastated zone, later tweeting that it was "difficult to not be emotional before this scene."

All was being done to care for survivors and "determine the facts, to demand justice and prevent new tragedies," he added.

The military said it was deploying 1,000 troops, including sniffer dogs, to the affected zone under orders from the president.

The disaster was the first big emergency faced by Bolsonaro and his government since he took office in early January, and perhaps one of the biggest disasters in Brazil's history.

Vale shares plunge

Vale has been shaken by the disaster, the second in three years it has suffered in the same state.

Workers at its mine had been lunching in an administrative area Friday when they were suddenly engulfed by millions of tons of muddy trailings -- a waste byproduct of the iron-ore mining operations.

The ruptured dam, 42 years old and 282 feet (86 meters) high, had been in the process of being decommissioned, and Vale said it had recently passed structural safety tests.

After overflowing a second dam, the vast muddy mass barreled down toward Brumadinho, population 39,000, but only glanced along it before spearing its way through vegetation and farmland, smashing houses and swallowing tractors and roads in its way.

Vale's CEO Fabio Schvartsman and Minas Gerais Governor Romeu Zema both expressed pessimism, warning the toll could rise.

"From now, the odds are minimal (to find more people alive) and it is most likely we will recover only bodies," Zema told reporters late Friday.

In Rio, Schvartsman spoke of a "human tragedy."

"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 said.

Vale shares plummeted on the New York stock exchange Friday, closing eight percent lower.

Brazil's environmental protection agency hit Vale with an initial $66.5 million fine over the disaster.

Minas Gerais state authorities said they were about to levy another penalty. They have already obtained a court order blocking $270 million of Vale funds in bank accounts with a view to using it for victim relief.

The mining company, one of the world's biggest, was involved in a 2015 mine collapse elsewhere in Minas Gerais that claimed 19 lives and is regarded as the country's worst-ever environmental disaster.

'Lessons not learned'

Would-be rescue volunteers were urged to stay away because of the slippery, perilous mud. Media were pressed not to use drones to avoid collisions with search and rescue helicopters.

"There used to be people here, houses. I'm just floored by this tragedy," Rosilene Aganetti, a 57-year-old resident in one of the affected villages, told AFP, pointing to an expanse of mud.

"Several of my friends who were in the Vale cafeteria are missing," she said, holding back sobs.

Another woman, Suely de Olivera Costa, desperately trying to find her husband who worked at the mine, accused Vale of "destroying Brumadinho and nobody is doing anything -- what will be the next town?"

The Brazil office of environmentalist group Greenpeace said the dam break was "a sad consequence of the lessons not learned by the Brazilian government and the mining companies."

Such incidents "are not accidents but environmental crimes that must be investigated, punished and repaired," it added.

While the death toll has yet to be fully established, the disaster at the mine could well rank among the worst recorded in Brazil.

In 2008, a moving mass of mud and rocks from an illegal iron ore mine slammed into the Chinese town of Taoshi, in northern Shanxi province, killing 262 people.

A mine collapse at a gold mine in Merriespruit, South Africa caused 17 deaths in 1994.