Bank Negara will not re-open its investigation into 1MDB despite the claim made by the United States Department of Justice (DOJ) that more than US$3.5 billion had been "stolen" from 1MDB.

Bank Negara Governor Muhammad Ibrahim said today the central bank has already taken all necessary action against 1MDB.

"We have completed our investigations into 1MDB based on the information and investigation papers.

"We have imposed a penalty on the company. We have taken all necessary action entrusted on us by the law and we have closed the investigation," Muhammad said at a press conference in Kuala Lumpur.

However, he said, the bank would cooperate with any investigating body looking into 1MDB.

Bank Negara had previously recommended that 1MDB be charged, based on its investigations.

However attorney-general Mohamed Apandi Ali rejected this and a subsequent appeal from the central bank.

The central bank later succeeded in fining 1MDB an undisclosed amount for failing to comply fully with directions issued under the Financial Services Act 2013.

No plan to strengthen financial rules

Meanwhile, Muhammad said there was no plan to strengthen Malaysia's financial regulations, like Singapore was doing in the wake of the 1MDB scandal, as the existing regulations to prevent money laundering and financial crime were robust.

Asked what mistakes were made that allowed huge sums of money to be deposited into a personal account, Muhammad said some rules had been flouted, and that the necessary action had been taken.

While no names were mentioned, this was an obvious reference to Prime Minister Najib Abdul Razak's RM2.6 billion donation scandal.

Apandi had said the donation, amounting to US$681 million in 2013, came from the Saudi royal family and that there was no wrongdoing by Najib.

However, the DOJ in its civil suits regarding 1MDB assets indicated that the funds were allegedly diverted from the state investment firm through intermediary companies.

On another matter, Muhammad brushed off a police report lodged by an Umno Youth leader against former central bank governor Zeti Akhtar Aziz.

"Anyone can do a police report, it's a free country. This is not the first time a police report has been made against the central bank."

Umno Youth vice-chief Khairul Azwan Harun had two weeks ago claimed that Zeti, former attorney-general Abdul Gani Patail and former Malaysian Anti-Corruption Commission (MACC) chief Abu Kassim Mohamed had conspired against Najib.

The police have said they would not pursue the case as the police report made was based on mere assumption.