Singapore announced Monday that it has seized a large number of bank accounts in a probe into alleged misappropriations related to an indebted Malaysian state investment fund.

Investigations of "possible money laundering and other offenses carried out in Singapore" in connection with the 1MDB fund have been continuing since mid-2015, said the Monetary Authority of Singapore and the Commercial Affairs Department, which polices white-collar crime.

Singapore is working closely with authorities in Malaysia, Switzerland and the United States in the investigation, the agencies said in a joint statement.

"In connection with these investigations, we have sought and are continuing to seek information from several financial institutions, are interviewing various individuals, and have seized a large number of bank accounts," they said.

"As investigations are still ongoing, we are not able to provide more details at this stage."

Singapore's stable economy and openness to foreign investment have made it a prominent destination for businesses in the region and farther abroad.

External investigations into 1MDB have indicated that $4 billion, earmarked for investment in economic and social development projects in Malaysia, may have been misappropriated from state-own companies.

Switzerland's top prosecutor has sought Malaysia's help after an investigation confirmed that some money was transferred into accounts held in Switzerland. The accounts were held by various former Malaysian public officials and both former and current public officials from the United Arab Emirates.

The Swiss office said in a statement Friday that criminal proceedings were opened last August against two former 1MDB officials and unknown individuals on suspicion of bribery of foreign public officials, misconduct in public office, money laundering and criminal mismanagement.

Malaysian Prime Minister Najib Razak, who formed 1MDB in 2009, became embroiled in the scandal after documents were leaked last year suggesting some $700 million deposited into his accounts may have come from entities linked to 1MDB.

Malaysian Attorney General Mohamed Apandi Ali cleared Najib of any wrongdoing last Tuesday, saying it was a private donation from the Saudi royal family.

Apandi said Saturday that his office will cooperate with Swiss authorities. 1MDB is mired in 42 billion ringgit ($10.1 billion) in debt and has been selling its assets to clear it.