US authorities are investigating whether Petrobras or its employees were paid bribes, adding to the mounting domestic corruption probes facing the Brazilian state-controlled oil company, people familiar with the matter say.

The US Department of Justice has opened a criminal investigation into the company, whose American depositary receipts trade in New York, while the Securities and Exchange Commission is pursuing a civil investigation, these people say.

Brazil’s biggest company has become the target of investigations by the federal police and prosecutors that is emerging as one of the country’s biggest corruption cases in history. Many of the alleged problems occurred when President Dilma Rousseff was head of the company before taking office in 2011.