(Adds details throughout, efforts to reach companies for comment, previous comment from Zelada's lawyer, link to timeline)
SAO PAULO, Aug 6 (Reuters) - Brazilian prosecutors on Thursday presented formal charges against Jorge Zelada, the former head of state-run oil firm Petrobras' international division, and five others, saying they favored U.S. company Vantage Drilling in a rig contract.
The most recent charges presented in Brazil's largest-ever corruption scandal included money laundering and corruption, and Zelada will stand trial with dozens of other engineering tycoons and former Petrobras executives if a judge accepts them.
One of the six charged by the prosecutor was Hsin Chi Su, chief executive of Taiwanese shipping firm TMT.
The federal prosecutor's office in the southern city of Curitiba said in a statement that Su and the others paid bribes of $31 million to Zelada, other ex-Petrobras officials, and Brazil's PMBD political party.
The PMDB, or Brazil Democratic Movement Party, is part of President Dilma Rousseff's governing coalition.
The prosecutor's office said that in exchange, Petrobras officials improperly favored Vantage Drilling for a contract with the oil company for the use of its Titanium Explorer rig. The award of the contract was rife with irregularities, prosecutors said.
Vantage Drilling did not answer calls for comment by Reuters to its executive office in Houston. Representatives of TMT could not be reached.
Vantage Drilling's CEO said on July 2, when Zelada was arrested and prosecutors first mentioned the company, that they had no evidence substantiating allegations of improper activity in connection with the awarding of the Titanium Explorer contract.
Zelada's lawyer Eduardo Moraes could not immediately be reached for comment but had said previously that his client's arrest was unnecessary and illegal.
Prosecutors also said international cooperation from authorities in Monaco had helped to uncover accounts held by Zelada amounting to 11.58 million euros ($12.7 million).
Zelada's accounts were still moving funds after he became ensnared in the corruption scandal, known popularly in Brazil as Operation Car Wash, prosecutors said.
They said evidence of irregularities in the Titanium Explorer contract included meeting records, e-mail exchanges and foreign bank transfers into and out of Zelada's accounts.
$1 = 0.9156 euros Reporting by Reese Ewing and Caroline Stauffer; Editing by Cynthia Osterman and Ken Wills