The State Comptroller's Office has been collecting evidence about overseas trips by some 15 ministers, including Prime Minister Benjamin Netanyahu, that were allegedly financed by private donors.

State Comptroller Micha Lindenstrauss began the probe in March after Channel 10 television published a report on overseas trips by Netanyahu and his wife, Sara, that were allegedly financed by private businessmen. Some of these trips took place when Netanyahu was serving as finance minister and as a regular MK.

Yesterday, investigators from the comptroller's office gathered material from the Foreign Ministry regarding Foreign Minister Avigdor Lieberman's trips.

This was a scheduled visit, not a surprise raid.

Also yesterday, Lindenstrauss took the unusual step of asking the Knesset State Control Committee to grant Nahum Levy - the former police officer who is handling the probe as head of the office's anti-corruption unit - the same investigative powers given to a state commission of inquiry.

Documents gathered

Levy has gathered documents and testimony from ministry legal advisors, budget directors and all officials who must be notified of a minister's impending absence.

He has also sought information from the travel agencies that arranged the plane tickets and hotel rooms for ministerial trips, and from various people involved in financing them.

Later, Levy plans to ask the security services for information as well, since they must be informed every time a minister goes abroad - whether on public or on private business - so that appropriate security arrangements can be made.

The probe covers the period from the middle of the last decade to the present. It is expected to continue for another few months.

Lindenstrauss has said in the past that, in principle, it is improper for private donors to finance public officials' trips abroad.

Legally, ministers and deputy ministers are bound by various rules formulated by the Asher Committee in the 1970s to prevent conflicts of interest.