Authorities in Brazil are beginning decontamination operations in areas flooded by toxic mud after an iron ore mine dam burst near the city of Mariana, Minas Gerais. Fifteen people are believed to have been killed in the disaster.

Those who survived the floods will be cleaned before being sent to shelters and hospitals. "People who are rescued will first undergo a process of washing with soap and water to avoid any problems for iron contamination," a spokesman for mining company Samarco told Brazil's Folha newspaper.

Forty-five people remain missing after the disaster at the Germano mine, union officials told local media.

Video footage on shows the town of Bento Rodrigues, about four miles from the dam, submerged in reddish mud, with cars turned on their side. A statement from municipal authorities in Mariana said that the dam ruptured at 4.20pm.

Hundreds of people from areas affected by the flooding have been taken to shelters and a sports stadium in Mariana, where they are being given food and medical care. Many are awaiting news of relatives.

Weberson Arlindo dos Santos described how Bento Rodrigues was completely submerged under the mud. "You try looking and see nothing. Only the canopy of mango trees," Weberson told O Globo. He said that all 15 houses in the town were destroyed, and that his wife 10-year-old daughter, parents and other relatives remain stranded in the area, with roads cut off by the mud slide.

Marcos de Souza Junior, 15, said he did not believe cries that the dam had burst, "until I saw the water break into my house", he told Folha.

Authorities said that the damn was holding water and residue from mining operations, which can often be toxic, containing metal filings, water, and chemicals. The dam burst near Gualaxo do Norte river, leading to fears of contamination.

The mine is owned by Samarco, a joint venture formed by Anglo-Australian BHP Billiton and Brazil's Vale company.

Andrew Mackenzie, the chief executive of BHP, said after news of the disaster: "Most of what happened there has been under the cloak of darkness. At daybreak, clearly we will do an awful lot more and give you further updates."

A spokesman for Samarco said that the cause of the breach was not yet known.