Prime Minister Ehud Olmert will likely be interrogated several more times by the police's National Fraud Unit on the new allegations against him, a former senior police investigator told The Jerusalem Post on Sunday. Cmdr. (ret.) Yosef Sedbon, who was the Israel Police's head of investigations between 1998 and 2001, is well-versed in criminal investigations against prime ministers and other high-ranking politicians. Sedbon oversaw inquiries into then-prime minister Binyamin Netanyahu, former president Ezer Weizman, and then-vice premier Yitzhak Mordechai. "A limited amount of time can be set aside for questioning on any given day, because this is the prime minister," Sedbon said, laying out some of the challenges faced by police when dealing with the head of government. "That's why the many questions are divided into separate interrogation sessions. This needs to be carefully planned to avoid giving away the direction of your inquiry to the prime minister," he said. According to Sedbon, the 90 minutes spent by Fraud Unit head Lt.-Cmdr. Shlomo Ayalon and two detectives at Olmert's residence on Friday morning were insufficient for police to put all of their questions to the prime minister. "More questions will arise. According to past experience, Olmert will be questioned several more times - I have no doubt whatsoever," Sedbon said. Also Sunday, Shula Zaken, Olmert's former bureau head and secretary of 30 years, was questioned for a second time in under a week at the Fraud Unit's Bat Yam offices. A sweeping court-ordered media ban has kept details and the names of other suspects in the investigation hidden from public view. Despite the ban, it has been reported that Attorney-General Menahem Mazuz issued an unusual permit for investigators to question Olmert on 48 hour's notice. While some reports have speculated that the permit's urgency was a sign of an especially severe and solid police case against the prime minister, Sedbon said it was issued because unplanned public exposure of the investigation last week had created a race against time. "In principle, when the police are allowed to carry out an undercover investigation, detectives can take their time. But when there is exposure, you need to act fast and take down initial testimonies from suspects. If you wait too long, the exposure ruins the investigation and allows suspects to coordinate their testimonies," Sedbon said. "All of the suspects need to be interviewed at the same time, and then have their testimonies cross-referenced. In an undercover investigation, documents and facts are assembled first, and only then are personal statements taken. Here, because of the exposure, the interviews took place first," he said. "But this does not mean there is a stronger-then-usual case," Sedbon emphasized. Questioning the prime minister is always going to be a daunting challenge, especially when he is Ehud Olmert, the former investigator added. He described Olmert as a sharp and fast-thinking powerful personality, with years of legal experience. "The investigators must go after the truth, while safeguarding the prime minister's honor," Sedbon said. He described Fraud Unit chief Lt.-Cmdr. Ayalon as "highly experienced and well-prepared" for the task. The location of Friday's interrogation - at Olmert's residence - had the potential to impact the psychological dynamics of the interrogation, Sedbon suggested. "Does being at home provide Olmert with an advantage, does he feel more comfortable? Possibly... but psychological fears, and all related questions have to be pushed aside. The investigators can't allow themselves to be influenced by that. "The prime minister doesn't have the option not to answer questions. The minute he turns silent, he gives up the right to be prime minister. According to what the police are saying publicly, Olmert has been cooperative," Sedbon said. "What is very unusual is the media gag. Police won't even allow Olmert's office to respond in full, which is rare," he added. Controversy over the strict media ban has been growing in recent days, prompting Police Insp.-Gen. David Cohen to defend the gag on Sunday. "We in the police are acting with a sole consideration in mind - the law and the rule of law. The investigation's interest takes precedent over the public's right to know - I know what I'm talking about," he said. Despite Cohen's strident defense of the court-imposed ban, "it can't last for many more days," Sedbon said, adding that he believed more details about the investigation would be revealed shortly. "Prime Minister Olmert is innocent until proven guilty. That's why the police has coordinated everything with the Attorney-General's Office. There is no room for error here," he said.