Yad Vashem has never funded any of Prime Minister Ehud Olmert's trips abroad, and a trip that police said the premier double-billed to Israel's Holocaust museum was apparently paid for by one of Yad Vashem's representative organizations abroad, the museum's head said in a document released Sunday. "Yad Vashem has never transferred any money to Mr. Olmert directly or indirectly, and has never funded any one of his trips," Yad Vashem chairman Avner Shalev wrote in a July 21 letter to the Ometz watchdog group, which had urged all organizations allegedly swindled in the "Olmertours" corruption probe to demand their money back. He added that the flight in question was apparently partially paid for by one of the societies for Yad Vashem abroad, and noted that those organizations were separate legal entities and subordinate to the laws of the countries in which they were based. "In light of the reports, we have asked the society to study the matter and act according to the findings of their inquiries," Shalev wrote. Olmert is suspected of billing multiple donors and organizations for the same overseas trips over several years, and using the excess - tens of thousands of dollars - to pay for personal flights abroad for himself and family members. Police have said that Olmert's Rishon Lezion travel agency, Rishon Tours, colluded in the scheme by sending copies of the same bill to numerous public bodies, including Yad Vashem, Friends of the IDF and an organization for mentally disabled children. All the organizations have expressed surprise at the allegations against the prime minister.