Seven bodies have been found, Avimar Melo, mayor of the municipality of Brumadinho, told the daily O Globo.

Out of the 300 people who were working at the site, only 100 have been accounted for, the news agency Agencia Brasil quoted Fabio Schvartsman, president of the mining company Vale, as saying.

Photos and video showed a torrent of mud flowing through a rural area in Brumadinho, in Brazil's south-eastern state of Minas Gerais.

The images show the sea of sludge inundating roads and homes. People could seen being plucked to safety by rescue helicopters.

The rupture of the dam released 13 million cubic metres of sludge, according to the newspaper Folha de Sao Paulo.

Vale installations were swept away, the Argentinian broadcaster Todo Noticias reported.

Schvartsman said he did not know the cause of the accident and added that the company had taken measures to boost security at dams.

President Jair Bolsonaro said he had created an emergency cabinet. "All possible measures" are being taken to help the victims, he said in a televised statement.

Bolsonaro said on Twitter he had dispatched his development, mining and environment ministers, as well as a civil defence official, to the region. The president himself was due to travel to Brumadinho on Saturday.

Minas Gerais already suffered a similar tragedy in 2015, when another mining dam collapsed in Mariana, resulting in 19 deaths.

Only 3 per cent of Brazil's 24,092 dams were surveyed in 2017, according to O Globo.

"Something is being done wrong," Agencia Brasil quoted Bolsonaro as saying in an interview.

Minas Gerais alone has 450 dams like the one that ruptured, the president added, saying measures were needed to prevent further tragedies.

Australian Associated Press