Brasilia, May 31 (RHC)-- In a blow to Brazil's interim government, another minister has stepped down after the leak of a new audio tape that reveals him trying to block a corruption investigation at the state oil company.  Transparency Minister Fabiano Silveira resigned on Monday from the government of acting president Michel Temer.

The presidential palace's media office confirmed that Silviera stepped down after a secretly taped conversation was released in which Silveira was heard talking to Senate President Renan Calheiros and Sergio Machado, the president of Petrobras subsidiary Transpetro.

On Monday, a protest rally was held outside the Transparency Portal offices in Brasilia, with the demonstrators chanting slogans and trying to block his entry into the building.  The anti-corruption protesters surrounded Silvieri's car as he arrived at the government offices after he officially stepped down.

Both Calheiros and Machado are being investigated in the Petrobras probe, which has implicated dozens of senior politicians and has led to the jailing of several top business executives.  Silveira was caught in the audio saying that the prosecution in the case was 'lost' and gave advice to Machado on how to protect himself from the investigation. 

A similar audio tape also released last week in Brazil, which led to the resignation of Planning Minister Romero Juca.  That tape was recorded only weeks before the lower house of parliament voted to impeach Dilma Rousseff.  Juca was heard saying suspended President Dilma Rousseff needed to be removed in an attempt to quash a vast corruption investigation that implicated him and other politicians.

Reacting to the leaks, Dilma Rousseff said the recordings prove that she has been a victim of a "political coup d'état."  Folha de Sao Paulo newspaper published an interview with Dilma on Sunday, in which she argued that that impeachment against her was designed to stop the investigation into the case.