Police entered the home of former Malaysian Prime Minister Najib Razak in Kuala Lumpur on Wednesday night, according to reports.
The reason for police entering the home was not immediately clear.
Reuters reported that witnesses saw around a dozen armed police enter Najib's home after he returned from prayers at a mosque. Bernama reported that 16 police vehicles and a truck were seen entering the residence around 10:15 p.m.
Video from the scene showed a large group of journalists gathered outside the home.
Najib was deeply unpopular and facing allegations of corruption and misappropriation of money from a state fund. His coalition party, Barisan Nasional, led the country since its independence 61 years ago. He was defeated by a coalition led by Mahathir, who came out of retirement to challenge Najib in the country's 14th general election.
Mahathir pledged to hold Najib accountable.
One twist in the election came when Mahathir embraced Anwar Ibrahim, his former deputy and later political foe, whom he once jailed on sodomy and corruption charges that critics said were politically motivated.
On Wednesday, Mahathir made good on a promise to secure a pardon for Anwar, whose case has dominated Malaysian politics for years.
Najib was under massive pressure in the runup to the elections, chiefly due to long-running allegations of corruption and misappropriation of money from a state fund, known as the 1Malaysia Development Berhad. He also lost political points with unpopular moves such as the introduction of a goods and services tax (GST), which many Malaysians feel has contributed to a higher cost of living.
Days before Parliament was dissolved and elections were called, Najib rammed through a bill in Parliament ostensibly targeted at curbing the spread of fake news. Critics said it was aimed at stifling free speech and dissenting voices, and Mahathir became one of the first people to be investigated under the law.
Amid calls for Najib to be prosecuted over the sprawling 1MDB corruption scandal, Malaysian immigration authorities barred Najib and his wife, Rosmah Mansor, from leaving the country.