In the latest development in Brazil’s Petrobras scandal, authorities have implicated a former presidential advisor and top Workers’ Party leader, bringing the case ever closer to the country’s pinnacle of political power.

On September 2, Brazilian police accused Jose Dirceu of money laundering, fraud, organized crime, and accepting bribes; part of ongoing investigations into corruption at state-owned oil company Petrobras, reported Reuters.

Dirceu is a founding member and top leader in Brazil’s Workers’ Party (PT) — the political party of current President Dilma Rousseff — and was also the Chief of Staff for former president Luiz Inacio Lula da Silva between 2003 and 2005. Prosecutors believe Dirceu — who was arrested in August — played a key role in organizing kickbacks and bribes at the center of the Petrobras scandal. He is the highest ranking PT official to be detained in relation to the case yet.

In 2012, Dirceu received a 10-year prison sentence after being found guilty of bribery in a voting corruption scandal. Prosecutors believe he continued to receive kickbacks from Petrobras while in jail. Before his arrest in August he had been living under house arrest.

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Investigations into corruption at Brazilian oil giant Petrobras, known as “Operation Car Wash,” began in March 2014 after allegations arose of top executives receiving bribes for issuing contracts at inflated prices. Since then, many top business and political elites have been implicated, with a July police raid resulting in asset-seizures of seven Senators — including former President Fernando Collor de Mello.

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Nonetheless, the charges against Dirceu represent perhaps the most significant blow to date against President Rousseff’s Workers’ Party, and again raises questions regarding her involvement in corruption at Petrobras. Not only did Rousseff chair Petrobras from 2003 to 2010 — when much of the corruption appears to have occurred — she also succeeded Dirceu as the Chief of Staff for Lula da Silva, who was recently implicated in an influence peddling scheme. Yet she has consistently denied any involvement in the scandal, and so far has not been implicated.

However, although investigations have been circling Rousseff for some time now — implicating a growing number of PT and Petrobras officials — it appears unlikely Brazil will follow the same route as Guatemala in the immediate future. In that country, investigations into a similar corruption scandal in the government’s customs agency eventually ensnared President Otto Perez Molina, leading to his resignation as well as the arrest of Vice President Roxana Baldetti.