The UK Court of Appeal Friday handed down a judgment allowing victims of Brazil’s biggest environmental disaster on record to pursue their claims in a British court. The claimants number over 200,000, making the case the largest group claim in the country’s legal history.

In November 2015, the Fundão tailings dam in the Brazilian state of Minas Gerais collapsed, releasing about 40 million cubic meters of toxic mineral waste across a 400-mile stretch of the country. The flood killed 19 people and decimated whole villages and communities, leaving thousands homeless and affecting even more via ecological damage to the Doce River, an important waterway that extends from Minas Gerais to the Atlantic. BHP Group, the defendant, is an Anglo-Australian mining company whose subsidiary, BHP Brazil, was part-owner of the dam. The claimants, numbering some 202,600, are all Brazillian and include, in part, members of the indigenous Krenak community, more than 500 businesses and 25 municipalities.

The Court of Appeal overruled a High Court judgment that refused British jurisdiction over the claims, citing a parallel action in a Brazilian court. On review, the panel of three justices found that “although the vast majority of the claimants have brought claims for loss of supply or contamination of water […] the losses claimed by individual claimants in these proceedings cover many additional heads of loss.”

Just three years after the collapse of the Fundão dam, the Brumadinho tailings dam also in Minas Gerais collapsed, this time killing 270 people. The ex-CEO of Vale, a mining company that was also part-owner of the Fundão dam, was charged with homicide by Brazilian authorities for his part in the latter incident.

BHP stated that it was “considering whether to seek permission to appeal the judgment to the UK Supreme Court.”