Mining company BHP has been found liable for a 2015 dam collapse in Brazil, known as the country's worst-ever environmental disaster, by London's High Court.
The dam collapse killed 19 people, polluted the river and destroyed hundreds of homes.
The civil lawsuit, representing more than 600,000 people including civilians, local governments and businesses, had been valued at up to £36bn ($48bn).
BHP said it would appeal against the ruling and continue to fight the lawsuit and has said many claimants in the London lawsuit had already been paid compensation in Brazil.
The dam in Mariana, southeastern Brazil, was owned by Samarco, a joint venture between the mining giants Vale and BHP.
The claimants' lawyers argued successfully that the trial should be held in London because BHP headquarters were in the UK at the time of the dam collapse.
A separate claim against Samarco's second parent company, Brazilian mining company Vale, was filed in the Netherlands, with more than 70,000 plaintiffs.
The dam was used to store waste from iron ore mining. When it burst, it unleashed tens of millions of cubic metres of toxic waste and mud. The sludge swept through communities, destroying hundreds of people's homes and poisoning the river.
Judge Finola O'Farrell said in her High Court ruling that continuing to raise the height of the dam when it was not safe to do so was the direct and immediate cause of the dam's collapse, meaning BHP was liable under Brazilian law.
BHP is expected to appeal the ruling. President of BHP's Minerals Americas, Brandon Craig, said in a statement that 240,000 claimants in the London lawsuit have already been paid compensation in Brazil.
We believe this will significantly reduce the size and value of claims in the UK group action, he added.
The lawsuit has seen conflicts between the UK firm representing the claimants, Pogust Goodhead, and BHP.
BHP has continuously denied liability and maintained that the London lawsuit duplicates legal proceedings already in motion in Brazil.
BHP and Vale established the Renova Foundation to provide reparations. They have offered cash compensation as well as housing in a new city intended to replace the devastated town of Novo Bento and have disbursed billions toward reparations.
As of June, reports indicated around 130,000 individuals in Brazil had reached financial settlements.
Claims have since surfaced that Pogust Goodhead pressured victims into settling for inadequate compensation.
Furthermore, accusations have been made against Pogust Goodhead for exploiting vulnerable populations in the aftermath of the disaster.
The former Brazilian ambassador said that conducting legal proceedings in London complicates efforts to resolve the situation locally.
