Dam bursts in Brazil's north-east

Four people have been killed and an unknown number are missing after heavy rainfall caused a dam to breach in Piaui state, in north-east Brazil.

State governor Wellington Dias has described the flooding around two towns which reached up to the level of three-storey buildings as a "tsunami".

Brazil's TV Globo reported almost 50bn litres of water escaped in less than an hour, devastating the valley below.

The search for missing people is due to resume on Friday.

The four people killed in the partial rupture of the dam included two young girls aged 10 and 12, a 72-year-old man and a 73-year-old woman, the state government said on its website.

Heavy rains in recent days swelled the reservoir behind the dam, increasing pressure that opened a 50m tear and eventually led to the rupture, the Piaui state government said in a statement.

The only video footage of the breach in the dam was taken with a mobile phone, says the BBC's Gary Duffy in Sao Paulo.

In the short rather indistinct images a torrent of water can be seen gushing outwards, our correspondent says.

People rushed to higher ground scrambling to rooftops as the floodwaters suddenly swelled a river.

"I heard a very loud thundering noise, and when the dam broke a huge column of water shot up 50m into the air, and when it came down it swept away everything in its way," said farmer Jose Maria Siqueira, quoted by the Globo TV website.

The number of houses swept away is not yet known but thousands of people were forced to seek shelter elsewhere. Crops and livestock have also been lost.

"It was a lot of water," said resident Antonio Antonino.

A torrent of water gushed outwards displacing thousands

"People were desperate, they were crying. I'm 60 years old, and I've never seen anything like this," Mr Antonino added.

Heavy rains in the area had caused water behind the dam to overflow two weeks ago, but it seems a build-up of pressure eventually forced a section to give way.

People still in the area say they heard a huge sound as the dam broke, and some scrambled into trees or onto the roofs of their homes for safety.

Some local people said they had been told it was safe to return to the area, and it seems certain questions will be asked about whether the best safety procedures were followed.

Flooding in the north and north east of Brazil, which began in April, is now said to have led to 56 deaths and displaced 426,000 people who are either staying with relatives and friends or are in public shelters.

BBC NEWS REPORT.