Brazil's state-run oil company Petrobras former president Maria das Gracas Silva Foster reacts during a session of a parliamentary commission investigating allegations of corruption in Petrobras, at the Chamber of Deputies in Brasilia March 26, 2015. REUTERS/Ueslei Marcelino

SAO PAULO (Reuters) - Brazil’s securities regulator formally accused eight former executives of state-run oil company Petroleo Brasileiro SA of corruption on Friday, as the world’s largest graft investigation stretches deep into its third year.

According to a legal filing by the CVM, Brazil's equivalent to the U.S. Securities and Exchange Commission, the accusations relate to possible irregularities in the contracting process for three drill ships. The accusations stem from an investigation started in March 2016, and include two former CEOs of Petrobras PETR4.SA, as the company is commonly known.

Petrobras is at the center of the so-called Lava Jato or “Car Wash” scandal, a massive corruption investigation that has sent dozens of top ranked executives and politicians to jail. The company, which is the target of 14 separate CVM inquiries, did not immediately respond to en e-mail requesting comment.

Among the accused in CVM’s filing are former Petrobras chief executives Maria das Graças Foster and José Sérgio Gabrielli; former services head Renato Duque; former supply chain head Paulo Roberto Costa; former international business head Nestor Cerveró; former CFO Almir Barbassa; former exploration and production head Guilherme Estrella; and former gas and energy head Ildo Sauer.

Several of the accused, including Duque and Roberto Costa, have already been convicted of separate corruption-related offenses. There was no public information immediately available regarding the timeline for the next steps in the legal proceedings.