BRASILIA/SAO PAULO (Reuters) - A federal court on Thursday ordered the arrest of the former chief executive officer of Bank of New York Mellon Corp’s unit in Brazil, a source with knowledge of the matter said.

The court in Brasilia issued the order to detain José Carlos Xavier de Oliveira, said the source, who spoke on condition of anonymity. The court declined to comment. All proceedings are under seal.

BNY Mellon declined to comment on the arrest order.

The CEO of Brazilian state development bank BNDES, Paulo Rabello de Castro, was questioned in federal police headquarters and released, according to a court document. Representatives for Rabello de Castro could not immediately be reached for comment.

Federal police served 100 search-and-seizure warrants on Thursday as part of an investigation into allegations of graft involving Postalis pension fund for post office workers. The Brazilian unit of BNY Mellon managed part of the assets held by Postalis.

A police statement did not identify any targets of the investigation, but said they included managers at the Postalis fund, executives at a foreign financial institution, listed companies and risk-assessment firms.

Postalis had suffered large losses as a result of embezzlement, police said in the statement.

Postalis said in an emailed response that it would not comment specifically on Thursday’s warrants, but that it hoped investigators would soon bring all facts to light.

The pension fund came under federal management last year because of the fraud allegations.

Representatives for the Brazilian unit of BNY Mellon confirmed that police had visited its offices on Thursday as part of an investigation, and that the bank was cooperating with authorities.

Last month, prosecutors asked the BNY Mellon unit to return 8.2 billion reais ($2.6 billion) to the pension fund. According to prosecutors, BNY had failed to monitor risks and did not comply with local asset-allocation rules. At the time, the unit called those accusations “unfounded.”