Singapore’s financial regulator is “closely studying” a report that said about US$4.4 billion ($5.98 billion) of suspicious transactions flowed through the city’s banks.

The island state’s largest lenders -- DBS Group Holdings Ltd., Oversea-Chinese Banking Corp. and United Overseas Bank Ltd. -- are among global firms that profited from “powerful and dangerous players” even after the US imposed penalties on the institutions, the International Consortium of Investigative Journalists said in an investigation published Sunday. The US$4.4 billion was processed by Singapore banks including DBS, OCBC and UOB, it said.

While the report doesn’t necessarily imply the transactions were illicit, the Monetary Authority of Singapore “will take appropriate action based on the outcome” of its review, it said in an emailed statement on Tuesday.

DBS shares fell 1.5% to S$19.70 as of 1:43 p.m. in Singapore, taking this year’s loss to 24%. OCBC dropped 0.6%, while UOB slipped 1%.

In responses to requests for comment, OCBC and UOB said their frameworks to detect illicit flows are “robust,” and that they keep improving their technology to help them identify money laundering. UOB added it complies “with all applicable laws, rules and regulations in the markets in which we operate.”

In an emailed statement, DBS said it has “zero tolerance for bad actors abusing the financial system” and that it is “generally very difficult to delay or intercept money in transit” unless there are sanctions on names or account freezes. “The normal process -- which happens behind the scenes –- involves subsequent investigations to establish suspicion, based on which the necessary action is taken.”