(Refiles to add attribution in the headline)
BRASILIA, Sept 6 (Reuters) - Brazil's Supreme Court has authorized prosecutors to investigate two ministers close to President Dilma Rousseff for allegedly receiving illegal campaign donations, one of them the treasurer of Rousseff's last campaign, Brazilian media reported.
Rousseff's chief of staff Aloizio Mercadante and Institutional Communications minister Edinho Silva have been linked to a corruption scandal at state-run oil firm Petrobras by one of the executives arrested in the case, according to Globo TV and O Estado de S. Paulo newspaper.
Senator Aloysio Nunes, from the opposition party PSDB, will also be investigated, the media said.
Spokespeople at the Supreme Court were not immediately available to comment on the reports.
The head of construction firm UTC Engenharia, Ricardo Pessoa, said in plea bargain testimony that some of the money resulting from the overpricing of Petrobras projects was donated to the campaign of several politicians, including Rousseff. Silva was the treasurer of Rousseff's campaign.
Mercadante and Silva have repeatedly denied any wrongdoing. When Pessoa's testimony became public in June, Silva said the 7.5 million reais donated by Pessoa to Rousseff's presidential campaign were legal and approved by the Supreme Electoral Court.
The Petrobras scandal has led to the arrest of dozens of lobbyists and executives of engineering companies accused of forming a cartel to fix prices and inflate the value of contracts with Petrobras to enrich themselves and politicians, mostly aligned with Rousseff's Workers Party.
Further investigations will be damaging to Rousseff, who is not among the dozens of politicians under investigation for taking bribes but has seen her popularity fall to single digits as a result of the scandal and a stalled economy.
Pessoa's testimony also led Brazil's chief prosecutor Rodrigo Janot to request the Supreme Court authorization to investigate President Dilma Rousseff's 2010 and 2014 campaign financing. (Reporting by Silvio Cascione)