BRASILIA (Reuters) - A leniency deal struck between the controlling shareholders of Brazilian meatpacker JBS SA and prosecutors may be partially revoked, threatening witnesses’ immunity but keeping their testimony, the country’s top prosecutor said on Monday.

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Prosecutor General Rodrigo Janot said at a news conference that billionaire meat tycoon Joesley Batista and a fellow state’s witness seemed to have inadvertently recorded a four-hour conversation discussing crimes not covered in their plea bargain. The audio was submitted to prosecutors on Thursday as an attachment to an unrelated matter, he said.

Joesley Batista and his brother Wesley previously confessed to bribing scores of politicians in plea bargain testimony that allowed them to avoid prosecution. With their help, prosecutors got a recording of President Michel Temer apparently endorsing hush payments to a possible witness in a graft probe.

Janot said the new audio was “very troubling” because it suggested the Batistas had not been forthcoming about all of their crimes. He also said the audio implicated someone at the Supreme Court of unspecified wrongdoing and suggested that a prosecutor in his office had aided the Batistas illegally.

Janot said evidence from their plea bargain testimony, which he has used to bring corruption charges against Temer, will stand regardless of whether witnesses lose immunity after an investigation of the new audio.

The prosecutor general is expected to bring a second wave of charges against Temer in coming weeks.

Questions about the Batistas’ testimony are likely to hang over the charges against Temer, making it easier for members of Congress to prevent the president from facing trial at the Supreme Court, as they did with earlier charges.

Temer declined to comment on the matter when asked by reporters in China.

J&F Investimentos SA, the holding company through which the Batista family controls JBS, said Janot had hastily interpreted the recording, which contained “considerations of hypotheses” and did not compromise the good faith of the witnesses.

The company agreed in May to pay a leniency fine of 10.3 billion reais ($3.3 billion) for its role in a political bribery scheme.

Since then, Joesley Batista resigned as chairman of JBS, but his brother Wesley remains chief executive and has been fighting efforts to remove him led by state development bank BNDES, another major shareholder in the world’s largest meatpacker.

Janot opened an investigation on Monday into revising the leniency deals of Joesley Batista and two other J&F executives, according to a document on his office’s website.

Since the plea deal, J&F has been racing to sell assets in order to reduce debt and pay the leniency fine.

In three months, the holding company has signed agreements to sell Havaianas flip-flops maker Alpargatas SA, dairy company Vigor Alimentos SA and pulpmaker Eldorado Brasil Celulose SA.

($1 = 3.1409 reais)