By Maria Pia Palermo and Guillermo Parra-Bernal
SAO PAULO (Reuters) - A Brazilian Federal Supreme Court justice has authorized the opening of an investigation into President Dilma Rousseff and her predecessor Luiz Inácio Lula da Silva for allegedly working to obstruct the course of a sweeping corruption probe, GloboNews news channel said on Tuesday.
According to GloboNews, Justice Teori Zavascki's ruling has given Prosecutor General Rodrigo Janot permission to look for additional evidence that Rousseff sought to name Lula to a cabinet post to help him avoid prosecution. In June, Zavascki barred the use of some wiretaps that showed Rousseff and Lula negotiating the cabinet appointment.
The news channel, without saying how it obtained the information, also said Zavascki authorized the opening of separate investigations against Aloizio Mercadante and Jose Eduardo Cardozo, two former Rousseff ministers, for similar allegations.
Press representatives at the STF and the Prosecutor-general's office in Brasilia could not immediately be reached for comment.
In a statement, Rousseff's press staff denied any attempt to obstruct justice, adding that the investigation will allow "the truth to prevail." Spokespeople for Cardozo and Mercadante did not immediately comment. In a widely sent email, Lula's lawyers said the former president "did not practice any act that could configure obstruction of justice."
The decision is likely to escalate pressure on the two leading political figures, whose Workers Party is ensnared in an ongoing bribes-for-state contracts scandal known in Brazil as "Operation Car Wash."
This is the first time that a Supreme Court justice has authorized an investigation into Rousseff, who is expected to stand impeachment trial on the Senate on Aug. 25 for allegedly doctoring budget accounts. Only the STF can authorize investigations against Rousseff and cabinet ministers, because they enjoy immunity from prosecution.
Late last month, a federal judge pressed charges against Lula for allegedly working to obstruct the work of investigators in the Car wash probe.
According to the judge's July 30 decision, Lula and another five people allegedly conspired in an attempt to buy the silence of a former executive at state-controlled oil producer Petróleo Brasileiro SA who was involved in the scandal.
(Reporting by Maria Pia Palermo and Guillermo Parra-Bernal; Writing by Guillermo Parra-Bernal; Editing by James Dalgleish)