RIO DE JANEIRO — A Brazilian judge suspended a nearly $50 billion lawsuit against mining firms responsible for the 2015 Samarco disaster Thursday, as negotiations between the companies and authorities moved forward.

The decision came as part of a ruling in which federal judge Mário de Paula Franco Júnior approved a road map toward a final agreement between prosecutors and mining companies Vale SA, BHP Billiton Ltd. and their joint-venture Samarco Mineração SA.

Federal prosecutors, regulatory agencies and the three companies have been locked in fierce litigation since Samarco’s Fundão tailings dam collapsed on Nov. 5, 2015, releasing an avalanche of mine waste. The incident is widely considered Brazil’s worst-ever environmental catastrophe and the largest failure of a mining dam.

Due to its scale — the disaster killed 19 people, wiped out villages below the dam and polluted hundreds of miles of rivers — authorities have struggled to come up with a definitive tally of the damage.

To that end, the partial agreement ratified Thursday called for three different groups of experts — two appointed by the court, one by the companies — to come up with studies that would assess the social, economic and environmental impacts of the disaster and evaluate the recovery programs under way.

Also as part of Thursday’s ruling, Judge Franco ordered Samarco and its parent companies to put up guarantees worth 2.2 billion Brazilian reais ($705 million).

In a statement, Vale expressed support for the decision, saying it “recognizes the complexity and importance of reaching a consensual solution to implement the necessary measures to remediate all the impacts” of the dam failure.

Write to Paul Kiernan at [email protected]