BHP reveals five mine dams at 'extreme' risk of causing damage and loss of life

Company says rating reflects potential extent of damage in event of collapse

Five dams used to store mining waste are at "extreme" risk of causing environmental damage if they fail, according to a review by BHP, the world's biggest mining company.

BHP said in a presentation on Friday that four tailings dams in Australia and one in the US were ranked at the highest level of risk, and had the potential to cause serious damage to the local environment and cause scores of deaths in the case of a collapse.