"In the ongoing criminal proceeding of the OAG, Mr Najib Razak is not one of the public officials under accusation," Andre Marty, spokesman for the OAG told the Nikkei Asian Review.
Meanwhile, in a statement late Monday, 1MDB said it has not been contacted by any foreign authorities on investigations into the firm's dealings.
"1MDB remains committed to fully cooperating with any lawful authority and investigation, subject to advice from the relevant domestic lawful authorities, and in accordance with international protocols governing such matters," it said.
Deputy Minister Aziz Kaprawi said the US$61 million was used for the 13th general election.
Najib has maintained he has never taken public money for personal use.
Apandi said Malaysia will assist the Swiss probe, although Deputy Prime Minister Ahmad Zahid Hamidi is unhappy the Swiss OAG for releasing its media statement.