São Paulo, Brazil (CNN)At least nine people are confirmed dead and 345 missing Saturday after a dam burst at a Brazilian iron mine, causing severe flooding in the southeastern state of Minas Gerais, according to local authorities.
The number of missing more than doubled since authorities' last report on Friday, hours after the rupture.
Aerial footage showed the city of Brumadinho covered in mud. Helicopters hovered near the ground as firefighters pulled people from the muck and airlifted them out of the area, video Friday from CNN affiliate Record TV shows.
Some 279 people have been rescued, Minas Gerais Civil Defense spokesman Officer Sargent Acquiles told CNN.
At least 200 rescuers were expected Saturday at the scene of the dam burst, doubling the prior day's tally, according to Minais Gerais state government.
Brazilian President Jair Bolsonaro was flying over the scene Saturday morning and is expected to hold a news conference after he lands.
Bolsonaro said the government's "main concern at this moment is to tend to the potential victims of this horrific tragedy," he tweeted at his official account.
'Beyond anything that I could imagine'
A "breach" on Friday caused mining debris to spill into the mine's administrative area, where employees were working, according to Vale, the Brazilian mining giant that manages the Feijao mine.
Authorities expect be able to contain the mud-like mine waste, called "tailings," within two days, according to the Brazilian National Water Agency (ANA). That's how long it's due to take the muck to reach the Retiro Baixo hydroelectric dam, 220 kilometers (135 miles) away, the agency reported.
An aerial view shows a collapsed bridge caused by flooding triggered by a dam collapse on January 25, 2019, near Brumadinho, Brazil.
ANA officials are "monitoring the mine tailings" and "coordinating actions" to supply quality water to the affected region, it said.
Authorities said Friday that 427 people had been in the iron mine when the dam burst.
Vale's president, Fabio Schvartsman, asked for forgiveness Friday "from all those affected and all of Brazilian society," according to a video sent out by the company.
"Unfortunately, the dam break (today) happened. This is inexcusable," Schvartsman said, adding the company will "do all possible" to aid victims.
"What just happened just now is beyond anything that I could imagine," he said.
Schvartsman also said the company had put an "immense effort" into improving its dams, especially after a similar mining disaster in 2015 in the city of Mariana.