The Marina Bay Sands (MBS) casino is being probed by the United States Department of Justice over whether anti-money laundering regulations were breached in the way it handled the accounts of top gamblers.
The Justice Department in January issued a grand jury subpoena to a former compliance chief of MBS, seeking an interview or documents on "money laundering facilitation" and any abuse of internal financial controls, according to a copy of the subpoena seen by Bloomberg News.
Prosecutors asked the former compliance head, as a person with knowledge of the casino's operations, to produce records related to any such violations including through gambling junkets and third-party lending using casino credit, the document shows.
The US inquiry, which people familiar with the matter said is likely in its early stages, is also seeking to establish if there was any retaliation against whistle-blowers, according to the subpoena.
MBS, owned by US billionaire Sheldon Adelson's Las Vegas Sands Corp, has one of the most profitable casinos in the world, accounting for more than a fifth of revenue and about a third of operating income at the US parent.
A spokesman for the US Attorney's Office in Las Vegas said she could not confirm or deny ongoing investigations. The subpoena also requested information on another former casino employee, whom sources said carried out fund transfers to high rollers.
The Singapore casino said any suggestion of inappropriate activity is taken seriously, and it has investigated every assertion of wrongdoing brought to its attention.
MBS also faces a probe in Singapore by the Casino Regulatory Authority into its money transfer policies. A spokesman for the agency declined to comment, adding that it has not received a request from the US Department of Justice in connection with MBS.
The regulator also said it is "committed to ensuring that the casinos in Singapore, including MBS, remain free from criminal influence or exploitation, and takes a serious view of any allegations of unauthorised money transfers".
Claims about these transfers surfaced in a lawsuit filed last year by Mr Wang Xi, who sued MBS seeking to recover $9.1 million that he said was sent to other casino patrons in 2015 without his approval. The Singapore Police Force is also investigating his complaint.
The Singapore regulator asked MBS to review its third-party transfer process, one of the people familiar with the matter said. Such transfers, when authorised, are legal and used by groups of gamblers to share winnings and losses at different foreign casinos.
Singapore requires casinos to implement internal controls and check the authorisation of fund transfers, as well as comply with requirements to prevent money laundering and terrorism financing, the regulator said.
"When allegations related to the mishandling of 'letters of authorisation' were made, the company thoroughly reviewed the matter," an MBS spokesman said in the statement. "The review concluded that no patron funds were transferred in a manner that was contrary to a patron's intent."