Federal prosecutors in Brazil have filed corruption charges against two former executives from commodities multinational Trafigura, a former executive at Petrobras and a middleman, over $1.5m allegedly paid in bribes for oil trading operations.

In a 146-page indictment, prosecutors in Curitiba in the southern state of Paraná said that former Trafigura executives Mariano Ferraz and Marcio Magalhães, middleman Carlos Herz and former Petrobras executive Marcus Alcoforado were involved in a corruption and asset laundering scheme that involved 31 oil trading operations between Trafigura and Petrobras, the Brazilian state-run oil giant. Magalhães, Herz and Alcoforado are all in custody.

“The bribes were paid to the former manager of external oil fuel sales of Petrobras by the Trafigura executives to obtain facilities, more advantageous prices and more frequent trading of fuel oil and oil products,” prosecutors said in a statement.

Financial operators laundered assets through hidden foreign accounts and made cash payments, they said.

Ferraz was previously handed a ten-year sentence last March for bribing a Petrobras executive to win contracts for another company, Decal do Brasil, but allowed to remain free on appeal.

He has Brazilian and Italian passports and was also a Trafigura executive when he was first arrested in October 2016. Magalhães was a country representative.

Their lawyers did not immediately reply to requests for comment. Other large global oil traders - Vitol, Glencore and Mercuria Energy Group – are also under investigation in Brazil.

The charges are the latest development in a long-running graft investigation called “Operation Car Wash” that since 2014 has resulted in the jailing of powerful politicians – including former president Luiz Inácio Lula da Silva – and executives, shaking Brazilian political and business establishments.

This is the 57th phase of the operation and was first unveiled on 5 December, when prosecutors said between 2009-2014, $31m was paid in bribes by oil trading companies to Petrobras employees to get sweetheart prices. Petrobras said then it would continue to assist and cooperate with the investigations and had dismissed employees involved.

The oil trading scheme lasted six years, prosecutors said on Friday, with indications that continued until the present and involved two other Petrobras employees. Investigations are continuing.

Mercuria has denied wrongdoing. Mercuria, Vitol and Glencore said they would cooperate with the Brazilian investigation, while Trafigura said it was reviewing the allegations.

Trafigura, Mercuria and Vitol said they have zero-tolerance policies for bribery and corruption. Glencore said it takes ethics and compliance seriously.

So far 11 arrest warrants have been issued in relation to this phase of Operation Car Wash, including one against a current Petrobras employee who has since been fired, and eight people arrested. Interpol alerts have been issued for three other suspects outside Brazil.