SAO PAULO--Vale SA and BHP Billiton Ltd., the owners of Brazilian mining company Samarco Mineracao SA, said Monday they agreed with Brazilian authorities to suspend for two years a 155 billion real ($41 billion) civil claim over the catastrophic 2015 collapse of a tailings dam while talks continue, disappointing investors who had been hoping for a final settlement of the suit.

The companies, federal prosecutors and the governments of the states of Minas Gerais and Espirito Santo will also ask to dismiss a separate civil claim, for 20 billion reais. The entire agreement needs to be approved by a federal court and by the federal government, BHP Billiton and Vale said in notes.

The dam, owned by Samarco and located in the Brazilian state of Minas Gerais, collapsed in November 2015, resulting in the deaths of 19 people and polluting more than 400 miles of waterways. Samarco, a joint venture half owned by Vale and half by BHP Billiton, shut down operations following the accident.

Samarco produced high-quality iron-ore pellets before it closed, and steelmakers are now paying miners a big premium for that type of ore. Samarco accounted for roughly one-fifth of the global iron-ore pellet market before its suspension, and financial markets are keenly interested in knowing when it will resume operations.

BHP Billiton declined to say when Samarco might restart.

Investors have also sought clarity on whether there will be changes to the future ownership of the operation, after several media reports over the past year said the companies were discussing whether Vale would take control of Samarco. BHP isn't currently in talks to sell its stake, a person familiar with the matter said on Monday.

The two civil suits, for 20 billion reais and for 155 billion reais, generated uncertainty over the final amount the companies will have to pay as deadlines for resolutions were postponed. With the smaller suit expected to be dismissed and the other talks extended, the agreement is a step in the right direction, but it doesn't clear up some key questions, some analysts said.

"Everyone was hoping for a final number and a little more visibility on the restart" of Samarco operations, said Jeremy Sussman, an analyst at Clarkson Capital Markets in New York.

The agreement brings more stakeholders into the negotiations, which will make the talks slightly more complex but "creates a more favorable environment for ongoing work and future negotiations," said Danny Malchuk, BHP Billiton's President of Operations, Minerals America, during a conference call.

Write to Jeffrey T. Lewis at jeffrey.lewis@wsj.com