Singapore's central bank said it was running a joint investigation with police into possible breaches of securities laws. The authorities also reportedly raided several brokerages.
The Monetary Authority of Singapore (MAS) said as part of its probe, conducted with the commercial affairs department of the Singapore Police Force, it had "obtained documents and items from several broking firms and trading representatives."
The MAS said it wasn't able to provide further information as the investigation was ongoing.
"As a matter of policy, MAS does not comment on its supervisory dealings with specific financial institutions," an MAS spokesperson said via email.
The spokesperson said the MAS statement was made in response to a request for comment on Thursday from local newspaper the Business Times, which on Friday reported that white-collar crime investigators had visited the trading floors of DBS Vickers, Maybank Kim Eng, OCBC Securities and Phillip Securities on Monday to take "certain items" as well as taking some people in for questioning.