One of the Wall Street giant's former directors has already been slapped with prohibition orders by regulators in Singapore and the US.

Singaporean authorities are reportedly scouring Goldman Sachs’ relationship with a scandal-warped Malaysian fund it helped raise billions of dollars for.

The city-state’s economic crime division and prosecutors have interviewed current and former executives who had worked on bond offerings from 1Malaysia Development Berhad, or 1MDB, the state-owned fund that has allegedly seen more than $4 billion siphoned from it since its launch in 2009.

The meetings are part of a wider probe into 1MDB-related fund flows, Bloomberg has reported, citing anonymous sources. 

Goldman Sachs declined to comment.

1MDB is under investigation in at least six countries including the US, Singapore and Switzerland. Authorities globally have alleged that some $4.5 billion has been looted from the fund by Malaysian officials and their associates, and that banks have helped wash the misappropriated cash. 

In March, Singapore’s regulator and de facto central bank, the Monetary Authority of Singapore (MAS), banned former Goldman Sachs director Tim Leissner from carrying out regulated activities for 10 years. In October, Leissner was also exiled from the US securities industry.

Last year, private banks BSI and Falcon were kicked out of Singapore over what were allegedly illicit dealings with 1MDB.

To date, five people have been jailed over their dealings with 1MDB.