Mahathir, who built much of his campaign by accusing Najib of corruption, vowed to control corruption and cronyism after the election. Security personnel from the building - which is owned by Desmond Lim, a wealthy Malaysian businessman and supporter of Najib - were cooperative."We are looking for government documents that may have been illegally taken", said a senior police officer, who requested anonymity as he was not authorized to talk to the media.
The 92-year-old prime minister in the report said Anwar could be given a seat in the cabinet once he was re-elected to parliament. He has been in hospital for a few months recovering from a shoulder operation. "The prime minister has given his assurance that the meeting of the pardons board will proceed as scheduled now at 11 am (0300 GMT) on Wednesday". He added that he would make the final decision about cabinet posts. Mahathir fired Anwar in the late 90s and oversaw his first jail conviction.
The volatile relationship between the duo has dominated the country's political landscape for over three decades.
When Mahathir was prime minister in the 1990s, Anwar was his deputy and clear heir-apparent. Anwar then started a movement known as Reformasi - reform to end the then ruling party's race-and patronage-based governance.
Faced with a leadership challenge, Mahathir used internal security laws to detain more than 100 opposition politicians, academics and social activists.
This communalist politics became more and more prone to corruption, cronyism and a crackdown on freedoms under Mahathir's successor, Najib.
In 2004, Anwar was freed but in 2015 was jailed again for five years for sodomizing a former aide.
Anwar and Mahathir agreed in 2016 to join forces with the aim of ousting scandal-hit Najib Razak and his Barisan Nasional (BN) alliance.
"We think that within a short while we will have a case against him", Mahathir said. "If there is no case against him, we don't go for detention without trial", Dr Mahathir was quoted as saying in the report. He and the fund have denied wrongdoing.
Mahathir blocked Najib from leaving the country last weekend.
In his interview with the WSJ at his office at Perdana Leadership Foundation here yesterday, Dr Mahathir also said that he expected criminal charges would be filed against former prime minister Datuk Seri Najib Tun Razak following an investigation into allegations that he siphoned off hundreds of millions of dollars from a state investment fund.