Brazil's state-run oil company Petrobras says it lost $2.1 billion because of inflated contracts and other costs related to a long-running kickback scheme.

Company executives released long-delayed audited financial results Wednesday night — including the write-down in local currency of 6.2 billion reais because of the graft scheme that Petrobras says operated from 2004 to 2012.

Federal prosecutors have called the scheme the biggest corruption case ever uncovered in Brazil. They stress that they are still investigating and says the scope of the case continues to widen.

Brazil's top construction and engineering companies are accused of paying bribes to Petrobras executives and politicians in return for winning inflated contracts. Prosecutors allege some of the money then flowed into the campaign coffers of the governing Workers' Party and its allies.