Brazil’s state-run oil company Petroleo Brasileiro SA said on Thursday it agreed to supply naphtha to Latin America’s largest petrochemical producer Braskem for two more months as the companies keep negotiating a long-term contract.

The contract has been under intense scrutiny after prosecutors charged executives at engineering group Odebrecht SA , Braskem’s biggest shareholder, with paying bribes to Petrobras executives to secure naphtha at a price that allegedly cost the oil company billions of dollars.

Braskem and Odebrecht have denied any wrongdoing, but Petrobras, Braskem’s second-largest shareholder, confirmed irregularities in the process of approving the 2009 contract.

(Reporting by Reese Ewing and Brad Haynes; Editing by Lisa Shumaker)