The police's anti-money laundering investigation unit quizzed Najib Abdul Razak's wife Rosmah Mansor for another four hours over the jewellery items seized from residences linked to the former premier.

Police sources told Malaysiakini that Rosmah arrived at the Menara KPJ in Kuala Lumpur at about 9.40am and left the premises at about 2pm.

"She entered the office through the fourth floor of the carpark building," said a source.

Last month, Rosmah together with her sons Norashman and Riza Aziz were also summoned for questioning.

During this session, Rosmah was interrogated for close to four hours regarding the ownership and purchase of the jewellery items.

In June, federal commercial crimes investigation department chief Amar Singh revealed that jewellery items worth RM440 million were seized from the Najib-linked properties.

These included 1,400 necklaces, 2,200 rings, 2,100 bangles, 2,800 earrings, 1,600 brooches and 14 tiaras.

Apart from this, police also seized 567 handbags worth more than RM51.3 million, 423 watches and 234 sunglasses valued at RM79 million and RM374,000 in cash.

"The investigation is far from over. As you can see, the number of jewellery confiscated is enormous. Police have to go through each of them.

"There will be another session in near future, most likely next week, but no date has been fixed yet," said the source.

He added that Rosmah's appointment with the police was supposed to be last week but it was postponed as she was summoned by the MACC.

Another source familiar with the probe said during last month's questioning, Rosmah was allegedly unable to furnish the police with all the details on where she obtained some of the jewellery.

"She alleged that some of the jewellery was sent to her house for review when she was not at home. So she had to provide more details regarding this matter," he told Malaysiakini.

Previously, it was reported that two foreign jewellers are seeking the return of their items, which are believed to be among those confiscated.

Last week, Rosmah was charged with soliciting RM187.5 million from a company in exchange for her assistance in securing an RM1.25 billion government contract.

On Oct 4, Rosmah claimed trial to 17 counts of money laundering involving over RM7 million.