In a press conference on Thursday outside Najib's residence, the former premier's lawyer said no documents had been seized during the raids, just personal belongings.
Najib made no arrests in his 1MDB investigation, and blocked both the USA and Switzerland from carrying out their own enquiries.
When asked when Najib would be called to have his statement recorded, Dr Mahathir said it was up to the police.
The reason for police entering the home was not immediately clear. He said the items were believed to have been taken for the objective of investigation under the Anti-Money Laundering and Anti-Terrorism Financing Act 2001, said Bernama.
More than a dozen police vehicles arrived at Najib's house shortly after he returned home from prayers at a nearby mosque, fueling speculation that he may be arrested after new Prime Minister Mahathir Mohamad warned that he could be charged soon over the 1MDB fund fiasco.
Late Wednesday, Mahathir, who gained a reputation as an authoritarian ruler during a previous stint in power between 1981 and 2003, told reporters arrests would only be made when there was clear evidence of wrongdoing.
Najib sacked dissenting ministers and senior officials, including then-attorney general Abdul Gani Patail, when the saga became public in 2015.
Mahathir has said he expects to run the government for one to two years but has signalled that the reins would be turned over to Anwar eventually.
"The focus on corruption is important because we need to get back money which is still in Switzerland, the U.S., Singapore and maybe Luxembourg".
Dr Mahathir also said the Government would work towards recovering funds belonging to 1MDB from overseas, including some RM17.8bil in the United States.
In the largest single action ever brought under the US government's Kleptocracy Asset Recovery Initiative, the US State Department is seeking to recover more than US$1bn in assets that were looted from the 1MDB fund and laundered through the US. He was dismissed from government and charged with corruption and committing "illegal" homosexual acts - allegations he has always denied.
There are no formal charges filed against Najib, but Mahathir has banned Najib, his wife and a number of former government officials from leaving the country.
Anwar's freedom is expected to ease fears of a growing rift within the newly formed coalition government, after differences erupted between supporters of Mahathir and Anwar over cabinet positions and Anwar's role in the party. We will declare the money is ours and will apply for it to be released to us.
Farage Offers Words Of Wisdom To EU's Tusk After Trump Outburst
Tusk went on to say the Iran deal remains "good for European and global security, which is why we must maintain it - despite the USA hesitation".