Former employees at BSI in Singapore have been named in various reports as having handled transactions for 1MDB, and although the Singaporean regulator did not refer directly to 1MDB in its statement, BSI Bank in Switzerland issued a statement in which it said it had ooperated with both Swiss and Singapore regulators in their investigations into the troubled wealth fund.
BSI also said its Group CEO Stefano Coduri had stepped down with immediate effect. Coduri had been in the role since 2012.
"The board of directors thanks Stefano Coduri's for his sense of responsibility and accepts his resignation," the statement said.
One of the BSI bankers named in the MAS statement, Yak Yew Chee, a former senior private banker, already faces a criminal probe in Singapore.
Yak, who left the bank in March, filed an affidavit with the Singapore High Court earlier this year denying any wrongdoing or receiving unlawful benefits from managing 1MDB accounts, according to a Reuters report.
Another of the names the MAS said on Tuesday it had referred to prosecutors, former BSI Bank wealth planner Yeo Jiawei, has reportedly been served with seven charges related to the 1MDB probe, including receiving benefits from criminal conduct, forgery and money laundering.
The forgery charge was related to Yeo allegedly signing a reference letter to another bank's compliance chief in order to help faciliatate a fund transfer.
Yeo has also been accused of asking another person named in the MAS statement on Tuesday, Kevin Michael Swampillai, BSI's head of wealth management services, to lie to police about a fund transfer.
A lawyer for Swampillai declined to comment. A lawyer for Yeo did not immediately return an emailed request for comment.
Two others named in the MAS statement, Hans Peter Brunner, the Singapore unit's former CEO, and Raj Sriram, the former deputy CEO, did not immediately return LinkedIn messages sent requesting comment.
No contact details could be found for Seah Yew Foong Yvonne, a former senior private banker at BIS, who was the sixth person named in the MAS statement as having been referred for potential prosecution.
Questions about movement of funds from 1MDB gained attention in July, when the Wall Street Journal reported that in 2013 nearly $700 million had flowed from the fund to Malaysian Prime Minister Najib Razak's personal bank account.
Najib has repeatedly denied wrongdoing and, under pressure from the outcry caused by the WSJ report, said the funds were a private donation from a Middle Eastern country he declined to name. He has denied benefiting personally from any of the funds.
In January, Malaysia's Attorney General Mohamed Apandi Ali said that Saudi Arabia's royal family gave Najib a $681 million gift, of which Apandi said about $600 million was later returned.
Apandi said that no criminal offense had been committed. But globally, investigations into 1MDB in locales as varied as U.S., Switzerland, Singapore and the Seychelles have continued.
The WSJ has reported that funds filtered from 1MDB financed Red Granite Pictures, a film production company co-founded by Najib's stepson Riza Aziz, which produced the film the Wolf of Wall Street.
The WSJ has also reported tha Riza used at least $50 million from 1MDB to purchase luxury properties in London, Los Angeles and New York. The WSJ said Riza had denied any wrongdoing.
In an emailed comment, Red Granite noted that it has received hundreds of millions in funding over the past six years from multiple sources, including U.S. commercial and investment banks, while generating nearly $1 billion in box office receipts.
"To its knowledge, none of the funding received by Red Granite was in any way irregular or illegitimate," the email said. "Red Granite is cooperating fully with all inquiries and is confident that when the facts come out, it will be clear that neither Riza Aziz nor Red Granite has done anything wrong."
—Nyshka Chandran contributed to this article.
—Follow CNBC International on Twitter and Facebook.