SAO PAULO — Brazilian prosecutors say they've launched an investigation into international trading companies suspected of paying more than $30 million in bribes to employees of state-owned oil company Petrobras.

Vitol, Trafigura and Glencore are among the companies mentioned in Wednesday's statement from the Federal Prosecutors office. Other trading companies are being investigated, but their names haven't been revealed.

Prosecutors say those three companies are suspected of paying bribes totaling $15.2 million for contracts to trade petroleum or lease storage tanks.

Vitol said in a statement that it has a zero tolerance policy toward bribery and corruption. Trafigura and Glencore had no immediate comment.

The investigation is part of Brazil's so-called "Car Wash" investigation into bribes from construction and other companies that was launched in 2014.