(Updates with Petrobras comments)

RIO DE JANEIRO, Sept 10 (Reuters) - A Petrobras manager was among the subjects of search warrants issued to police on Thursday, part of a years-long investigation into alleged corruption at the Brazilian state-controlled oil firm, according to court documents seen by Reuters.

Brazil's federal police served 25 search warrants as part of the sweeping "Car Wash" probe, one of the world's largest-ever corruption investigations. No arrests were made on Thursday.

The warrants were related to 7.7 billion reais ($1.45 billion) in suspected fraudulent foreign-exchange transactions carried out between 2008 and 2011 at Petrobas, formally known as Petroleo Brasileiro SA

One warrant was for Larry Carris Cardoso who was in a "relevant managerial" position in the finance department, according to a copy of the warrant request seen by Reuters.

The inclusion of a Petrobras manager in the latest probe underscores the difficulties Brazilian authorities have had in cleaning up the sprawling firm.

Prosecutors say Cardoso was responsible for 228 foreign exchange transactions worth approximately 2.8 billion reais, in which some of the money may have been skimmed off the top and kicked back to corrupt actors.

Cardoso did not immediately respond to requests for comment sent by email and LinkedIn. In a May document submitted to the U.S. Securities and Exchange Commission by Petrobras, he is cited as its Loans and Financing Administration General Manager.

Petrobras said in a statement it is conducting internal investigations, adding it "actively collaborated with the authorities in the probe and provided information that resulted in (today's) operation."

It also said in a later statement on Thursday that it had made a decision to fire one of the employees cited in the investigation but did not name the employee.

Various branches of Petrobras have been under investigation since 2014, when Car Wash began. Petrobras has since beefed up its compliance and launched a series of internal investigations in an attempt to weed out graft.

(Reporting by Sabrina Valle, Rodrigo Viga and Gram Slattery; Editing by Lisa Shumaker and Edwina Gibbs)