The chief investigator probing the assassination of former Lebanese Prime Minister Rafik Hariri said Wednesday he is more confident than ever that those allegedly involved in the killing will be brought before a tribunal to face justice. In his final appearance before the UN Security Council, Belgian prosecutor Serge Brammertz said that progress made in the last few months has enabled UN investigators to identify "a number of persons of interest" who may have been involved in some aspect of the crime - or knew about the preparations. But he said he cannot predict when the investigation will be complete because that depends on the final results of several ongoing projects, which he did not disclose, and on the abilities of the prosecutor of the new UN-backed tribunal that will try suspects in the Hariri assassination. "It's a very complex puzzle of elements which altogether are the crime as such," Brammertz told reporters afterward. "So we have answers and indications on some of these questions, but others are still open, and to make a final assessment of responsibilities, you really need to know the full picture." Investigators have previously confirmed that a single blast from a Mitsubishi Canter van packed with 3,960 pounds (1,800 kilograms) of high explosives was detonated "most likely" by a male suicide bomber in central Beirut on Feb. 14, 2005, killing Hariri and 22 others. Brammertz said the UN International Independent Investigation Commission has "a certain understanding" of who some people behind several aspects of the assassination may be, and it its starting to have "a much better picture than some time ago" of the people who actually carried out the crime. "And then you have ... the crime scene as such, where we really strongly believe we know what happened," he said. Investigators also strongly believe "that it's in the political context that the motive has to be found," Brammertz said. The first UN chief investigator, Germany's Detlev Mehlis, said the plot's complexity suggested that Syrian and Lebanese intelligence services had a role, but Brammertz has not echoed his view. He said Wednesday that it was not his mandate "to confirm or not confirm the opinion of my predecessor." Syria denied involvement in Hariri's assassination but was forced to withdraw its troops from Lebanon, ending a 29-year presence. Four pro-Syrian Lebanese generals have been under arrest for almost two years for alleged involvement in the murder. While Brammertz refused to be drawn out about many specifics in the investigation, he told the Security Council, "When I am asked whether I am satisfied with the progress made so far, my answer is absolutely yes." "Important results have been achieved in many areas of the investigation despite the numerous challenges the commission has faced," he said. "Based on the progress made in recent months, I am more confident and optimistic than ever that the investigation can be concluded successfully," Brammertz told council members. The Security Council has unanimously approved Brammertz' nomination to head the Yugoslav war crimes tribunal in the Hague, Netherlands, starting Jan. 1. UN Secretary-General Ban Ki-moon appointed former Canadian prosecutor Daniel Bellemare to head the Hariri probe and he told reporters Wednesday that "we are committed to ensure a seamless transition." The council adopted a press statement commending Brammertz "for his outstanding work" and leadership "in advancing the investigation" and reiterated its support for the commission. Brammertz told reporters that his only objective during the two years he led the investigation - under difficult circumstances and seeing the suffering of many Lebanese people - "was to help in advancing this investigation as much as possible." "I very, very much hope that the investigation will continue in the same direction, and at the end of the day, this investigation is successful and that a tribunal can put an end to impunity, and that political assassination will not be any more one of the major problems in your country," he told a Lebanese reporter. Brammertz said in his final report that the commission confirmed its hypothesis that "operational links may exist" between the perpetrators of 18 other targeted assassinations and bombings in Lebanon. "Confirming these operational links will be one of the commission's highest priorities in the months to come," he told the council. The most recent assassination, of Parliament member Antoine Ghanem on Sept. 19 - just three days after he returned to Beirut from a prolonged trip overseas - showed that the perpetrators were able to conclude their surveillance and arrange a car bomb on short notice, he said. This suggests "that those perpetrators have important operational capabilities - and probably still have - in Beirut," Brammertz said.