(Adds Petrobras confirming investigation)
BRASILIA, March 21 (Reuters) - Brazil's Petroleo Brasileiro SA is investigating practices in its human resources department that may have left the state-run oil producer vulnerable to billions of reais in liabilities, newspaper Valor Economico reported on Monday.
João Elek, governance head of the company known as Petrobras, is leading the internal probe after an anonymous report of 11 potentially controversial measures taken by the department in recent years, which could have included special treatment to union members at top management levels, Valor said.
A Petrobras spokeswoman confirmed the investigation in an emailed response to Reuters without giving further details.
The HR department has been managed by executives linked to an oil workers union since 2003, when Luiz Inacio Lula da Silva, of the Workers' Party, started his first term as president, according to Valor.
Petrobras is at the center of a massive corruption probe that has shaken Brazilian politics over the past two years. Some of the nation's most powerful executives and politicians are in jail or under investigation for billions of dollars in rigged contracts and kickbacks to parties in the ruling coalition.
In investigating its HR practices, the company will look at potential conflicts of interest in collective salary negotiations held by managers linked to unions.
Terms of some agreements may cost Petrobras tens of billions of reais in legal liabilities, according to the report. The newspaper reported that the exact numbers remained unknown. (Reporting by Silvio Cascione; Editing by Jeffrey Benkoe and Lisa Von Ahn)