Former Prime Minister Datuk Seri Najib Tun Razak could be charged under the Malaysian Anti-Corruption Commission (MACC) Act 2009 if he failed to turn up at the agency headquarters in Putrajaya today.
USA investigators say Najib's associates stole and laundered $4.5 billion from the fund, some of which landed in Najib's bank account.
Najib has said US$681 million of funds deposited in his personal bank account were a donation from a Saudi royal, rebutting reports that the funds came from 1MDB.
A government official has said Najib could possibly be detained after giving his statement to Malaysia's Anti-Corruption Commission. Najib has denied any misconduct related to 1MDB and was cleared by the attorney-general at the time.
Among those seen arriving were former Attorney General Tan Sri Abdul Gani Patail; Federal police Special Branch senior officer Datuk Abdul Hamid Bador; and MACC's chief commissioner Datuk Seri Mohd Shukri Abdull. Mahathir, 92, was prime minister for 22 years until 2003 but emerged from retirement to join hands with former political foes amid anger over the 1MDB scandal.
"We wanted to bring back money that was stolen back to Malaysia".
What has been missing to date: investigators in Malaysia working with them on the case.
These complaints alleged that more than US$4.5 billion was diverted from 1MDB and laundered through a web of shell companies and bank accounts located in the United States and elsewhere.
On May 18, police seized 284 boxes filled with designer handbags, watches, jewellery and cash in various currencies from three condominiums at Pavilion Residences in Kuala Lumpur.
Amar Singh Ishar Singh, director of the national police's Commercial Crime Investigation Department (CCID), confirmed that the searches were tied to the 1MDB case.
Najib and Rosmah have been barred from leaving Malaysia.
"I'm coming back to finish what I haven't finished", he said.
Mansor says the family will cooperate, but that authorities should not "be feeding social media trolls".
"It is our hope that the authorities would observe the rule of law and due process, to avoid a premature public trial", Rosmah's lawyers, Valen, Oh and Partners, said in a statement on her behalf.
Describing the governing Pakatan alliance as being inexperienced, Mahathir also announced the formation of a "Council of Eminent Persons" to advise on economic and financial matters during the transition period.