Ari Harrow, the former chief of staff of Prime Minister Benjamin Netanyahu, was questioned under caution by police for 15 hours on Thursday as part of an examination of information regarding the prime minister.
At the end of the interrogation, Harrow was sent home on a five-day house arrest and was barred from contacting anyone involved in the case.
Harrow was detained at 5:30am Thursday at Ben-Gurion International Airport after returning from Madrid and was taken to the offices of the police's National Fraud Investigations Unit.
At first, Harrow was merely giving testimony but later he was informed by his interrogators that he was being questioned under caution.
Harrow's questioning comes a few days after Attorney General Avichai Mandelblit announced that information pertaining to Netanyahu will be examined by authorities before a decision can be made on whether to launch an official police investigation on the matter.
The preliminary measures taken so far have been conducted under a media blackout, and what little has been reported so far remains unconfirmed.
Harrow's lawyer, Roi Blecher, said that "naturally, because this is an ongoing investigation, I cannot comment on the details."
Last December, Harrow was questioned under caution for hours on suspicion he was acting in a conflict of interests. He was released on a five-day house arrest at the time as well.