1MDB is at the centre of money-laundering probes in at least six countries, including Switzerland, the United States and Singapore. A total of $4.5 billion was misappropriated by high-level officials of the fund and their associates, according to civil lawsuits filed by the U.S. Department of Justice.
The Swiss Attorney General's office said on Tuesday it had launched investigations into two officials from PetroSaudi - which ran an energy joint venture with 1MDB from 2009 to 2012.
The investigations, first launched in November 2017, were linked to "suspicions of criminal mismanagement, fraud, bribery of foreign public officials, aggravated money laundering and misconduct in public office," the Attorney General's office said.
"One of the two suspects is also suspected of document forgery," it added, without identifying either suspect. It said it had kept the inquiries under wraps to avoid jeopardising the investigation.
Malaysian Prime Minister Najib Razak, who set up 1Malaysia Development Berhad (1MDB) in 2009 and served as chairman of its advisory board, has denied any wrongdoing. He is seeking re-election on May 9.
PetroSaudi's solicitors Carter-Ruck said the company was aware of an inquiry by Swiss authorities related to 1MDB, and was ready to cooperate fully.
"PetroSaudi denies any wrongdoing in connection with its Joint Venture with 1MDB and it rejects any claims that it, or any of its officials, are involved in the misappropriation of funds from 1MDB," the law firm said in an email.
The fund issued a statement calling for "all parties to refrain from politicising any alleged investigation by the Swiss authorities on non-Malaysian nationals, and, during this sensitive general election period, desist from trying to create links to 1MDB for political gain."
"We wish to state in the strongest possible terms that 1MDB is not the subject of any criminal investigation either in Malaysia or internationally," it added in a statement.
Swiss prosecutors are also reviewing a criminal complaint filed against two former colleagues and an alleged accomplice by Xavier Justo, a former director of PetroSaudi International Ltd and a key figure in the 1MDB affair.
Justo has told Reuters he was trying to clear his name after being jailed in Thailand for blackmailing his former employer over its ties to scandal-hit 1MDB.
It was documents that Justo leaked after he left PetroSaudi in 2011 that triggered the international investigations.
(Reporting by Michael Shields in Zurich, additional reporting by Praveen Menon in Kuala Lumpur, Alexander Cornwell and Rania El-Gamal in Dubai Editing by Andrew Heavens) ((Michael.Shields@thomsonreuters.com; +41 58 306 7461; Reuters Messaging: firstname.lastname@example.org))