(Reuters) — An anti-money laundering body in the Philippines has filed charges against five officials of an RCBC bank and a former treasurer who "willfully ignored" suspicious activity that led to tens of millions of dollars vanishing after a heist on Bangladesh's central bank.

Unknown cyber criminals tried to steal nearly $1 billion from the Bangladesh Bank in February in what was one of the biggest bank heists ever.

They succeeded in transferring some $81 million via an account at the New York Federal Reserve to four accounts in fake names at a branch of Rizal Commercial Banking Corp. in Manila. Most of the cash was quickly withdrawn and laundered through multiple channels.

In a 97-page complaint to the justice ministry, the Anti-Money Laundering Council said former RCBC Treasurer Raul Tan, three retail banking officials and two workers at the branch where cash was withdrawn were guilty of money laundering because they should have noticed something was wrong and intervened immediately.

Only about $15 million has been recovered and returned to Bangladesh, with a further $2.7 million frozen. The rest of the funds changed hands several times and vanished in the Philippines casino industry.

No arrests have been made despite investigations by the U.S. Federal Bureau of Investigation, Interpol, Bangladesh police and authorities in the Philippines.

Mr. Tan resigned as the bank's treasurer in April.

The AMLC complaint, seen by Reuters on Wednesday and filed on Nov. 18, covers three retail banking workers and two customer relations officers at its Jupiter branch in Makati City. The complaint was based on evidence gathered from the bank.

"Tan was in a position to order enhanced due diligence based on the red flags," it said.

"Tan could have convened the anti-money laundering committee to act on these red flags," the AMLC said, adding Mr. Tan "willfully ignored them and failed to conduct thorough investigation", as required by law and the bank's regulations.

Mr. Tan's actions showed he had "knowledge that the funds transacted represented the proceeds of an unlawful activity," it said.

RCBC in a statement said its own probe had found no official from the head office involved in the transaction, which was initiated and carried out by the Jupiter branch.

"We welcome the charges as an opportunity to conclusively prove that our executives acted properly and had no knowledge or participation in any money laundering," President and CEO Gil Buenaventura said.

A long-time RCBC client, casino owner and agent Kim Wong, had admitted during a Philippines Senate inquiry that he received millions of the loot from two Chinese gamblers but did not know it was stolen. He denies involvement in the heist and has returned $15 million of around $35 million he said he received.