KUALA LUMPUR: Malaysian police on Thursday raided properties owned by former Prime Minister Najib Razak as part of a renewed investigation into the 1MDB investment fund scandal.

Police searched Najib鈥檚 home for more than six hours, looking for documents in connection with the multibillion-dollar corruption inquiry.

Witnesses said that bags and boxes of personal items were seized by the authorities.

1MDB became one of the biggest corruption cases in the world when it emerged in 2015 that $4.5 billion had been stolen from a state investment fund run by Najib.

More than $700 million was alleged to have been siphoned off into Najib鈥檚 personal bank accounts, a charge the former prime minister denies.

Harpal Singh Grewal, a former lawyer for Najib, told reporters: 鈥淭he search is supposed to be under the money laundering act 鈥� (but) they found nothing incriminating.鈥�

A photo of Najib sleeping on a couch went viral, prompting criticism of the raid.

鈥淎s former victims of early dawn police raids, I must stress my disagreement in ransacking any home at such an ungodly hour,鈥� said Nurul Izzah, an MP and daughter of Anwar Ibrahim, leader of the People鈥檚 Justice Party.

However, Eric Paulsen, executive director of Lawyers for Liberty, said: 鈥淭his is a real crime, involving billions in public funds, not some frivolous social media or sedition comments that led to a house raid. Have some perspective,鈥� he wrote on Twitter.

Professor James Chin, a Malaysia expert at Tasmania University鈥檚 Asia Institute, said the raid was necessary, 鈥渙therwise documents will be destroyed.鈥�

Malaysia鈥檚 Prime Minister, Mahathir Mohamad, has placed Najib under house arrest and ordered a renewed investigation into the 1MDB scandal.

Last week, Najib and his wife, Rosmah Mansor, were stopped from leaving the country when he decided to fly to Indonesia for 鈥渁 short break鈥� after losing the election.

Gani Patail, the former auditor-general of Malaysia who ordered the audit on the 1MDB case, has told Mahathir that he was on the verge of prosecuting Najib when he was sacked by the former PM.

A declassified document compiled by Gani revealed a complex network of international money laundering involving sums much larger than previously thought.

鈥淚 have been briefed by police and the auditor-general and it is clear there was more wrongdoing than what was known by the public and me,鈥� said Mahathir.

The auditor-general鈥檚 report corroborates the findings of the US Department of Justice last year. The department had seized assets bought with the 1MDB funds, including Van Gogh paintings, jewelry and properties in New York.

In a press conference on Wednesday, Mahathir vowed to work with authorities in Switzerland, the US, Singapore and other jurisdictions 鈥渢o help recover the (1MDB-laundered) money, which can help Malaysia pay off its debts.鈥�

鈥淭here is plenty of evidence, not only on Najib, but also other people who are involved,鈥� he said. 鈥淲hen it is necessary to arrest, we will make the arrest according to the law.鈥�