Australian mining company BHP informed that the mud spilled from the collapse of two of its dams is not toxic. The UN reported on Thursday that the dam burst at the Samarco mine released a flood equivalent to "20,000 Olympic swimming pools of toxic mud".

BBC reports that the accident in Minas Gerais had left 13 people dead. Eleven people are still missing, but are now presumed dead. In addition to that, several villages within the area have been destroyed.

BHP, however, denied the claim of the UN. The mining giant said in an official statement that the waste water in the dam, which is a by-product of iron ore extraction known as tailings, does not have any harmful effect on humans.

The Australian mining giant added that the tailings which entered the Rio Doce are composed of clay and silt. According to the company, iron ore is abundant in the region. The waste, the report said, would only behave in the "natural way" that normal soils do.

The dam at the Samarco mine is jointly owned by the Australian company, as well as Brazil's mining giant, Vale. The dam burst on November 5. Investigations were done by both the UN and Brazil's local environment agency. They said that the red-looking sludge contains toxic chemicals and poses threat to humans.

The state water agency added that the arsenic levels found in the samples are at 10 times the legal limit.

In addition to that, the UN human rights agency reported that both mining companies have not stepped forward into taking the necessary actions to prevent the harm that was caused by the toxic waste, The Wall Street Journal said.

This incident has been dubbed as Brazil's "worst mining accident." Residents who were affected said that the flood came "without warning" and that they had very little time to prepare for the disaster. Many of them had to run for their lives and leave their homes when they realized that the Fundao Dam was collapsing.

Meanwhile, Samarco has agreed to pay the Brazilian government the sum of 1bn reais ($260M) as a form of compensation.

The money received will be used to cover the costs of the initial clean-up of the affected towns, as well as the rivers. In addition, the amount will be also used to offer some compensation to the victims and the families of those affected by the dam's collapse.