BRASILIA (Reuters) - A judge in Brazil has temporarily suspended criminal proceedings against 22 people and four companies accused of killing 19 people in the 2015 Samarco mine disaster, over the legality of phone intercepts between executives involved and other evidence.

Vale SA and BHP Billiton, joint owners of the Samarco iron ore mine, are among those accused of crimes related to a burst tailings dam that unleashed a torrent of waste in what is considered to be Brazil’s worst-ever environmental disaster.

A judge in Minas Gerais state is considering whether to dismiss the case on claims from two Samarco executives that phone data, instant messages and emails were collected outside of the time period legally authorized, according to a legal order accessed by Reuters and dated July 4.

The criminal actions are separate from negotiations over a $47 billion financial settlement pending in civil proceedings.

Judge Jacques de Queiroz Ferreira said in the order that the arguments from defendants, former Samarco President Ricardo Vescovi and ex-director of operations and infrastructure Kleber Luiz de Mendonça Terra, raised grave questions and could result in the entire case being thrown out.

The judge accepted a request from federal prosecutors that telephone companies clarify whether wiretaps occurred within the legal parameters.

After receiving the requested information, prosecutors will have 10 days to act followed by an equal period for the defense to respond before a ruling is made.

The Samarco catastrophe released thick reddish-brown sludge into the Rio Doce, one of Brazil’s main rivers, killing fish and fouling water supplies for hundreds of kilometres (miles) before reaching the Atlantic Ocean.

BHP and Samarco executives have said that it is increasingly unlikely that the mine will restart operations this year.