Israeli Prime Minister Benjamin Netanyahu has been quizzed for more than three hours by police investigators, opening what could be a politically-damaging criminal investigation into suspicions he improperly accepted gifts.
Mr Netanyahu has repeatedly denied wrongdoing but the arrival of the national fraud squad indicated questions raised about him are considered serious enough to merit an investigation.
Police said Mr Netanyahu was questioned "under caution", a term signalling he is a suspect.
Police spokeswoman Luba Samri said Mr Netanyahu was questioned on "suspicions he received benefits". She said there would be no further details released at this stage.
The police team did not speak to journalists but Israeli media said they are looking into suspicions Mr Netanyahu inappropriately accepted expensive gifts from two businessmen.
A black screen had been placed in front of the building in apparent anticipation of the investigators' arrival and to obstruct the view of journalists seeking to film them.
Mr Netanyahu has denied what he calls "baseless" reports that he received inappropriate gifts, a point he reiterated at a meeting of his Likud faction earlier on Monday.
"We've been paying attention to reports in the media, we are hearing the celebratory mood and the atmosphere in the television studios and the corridors of the opposition, and I would like to tell them, stop with the celebrations, don't rush," he said.
"There won't be anything because there is nothing."
Israel's Channel 2 TV has said Mr Netanyahu accepted "favours" from businessmen in Israel and abroad and that he is the central suspect in a second investigation that also involves family members.
The newspaper Haaretz said billionaire Ronald Lauder, a long-time friend of Mr Netanyahu, was linked to the affair.
Channel 10 TV has reported that Mr Netanyahu's oldest son, Yair, accepted free trips and other gifts from Australian billionaire James Packer.
In October, Mr Lauder was summoned by police for questioning "related to a certain investigation conducted by them and in which Mr Lauder is not its subject matter," said Helena Beilin, Mr Lauder's Israeli attorney.
"After a short meeting, he was told that his presence is no longer required and that there shall be no further need for additional meetings."
Israel's Justice Ministry declined to comment.
A campaign is under way by Erel Margalit, an opposition lawmaker of the Zionist Union party, seeking for Mr Netanyahu to be formally investigated over suspicions of prominent donors improperly transferring money for the prime minister's personal use as well as reports that Mr Netanyahu's personal attorney represented a German firm involved in a 1.5 billion US dollars (£1.2 billion) sale of submarines to Israel.