ULM, Germany -- Khaled el-Masri says his strange and violent trip into the void began with a bus ride on New Year's Eve 2003. When he returned to this city five months later, his friends didn't believe the odyssey he recounted. Masri said he was kidnapped in Macedonia, beaten by masked men, blindfolded, injected with drugs and flown to Afghanistan, where he was imprisoned and interrogated by U.S. intelligence agents. He said he was finally dumped in the mountains of Albania. A Munich prosecutor has launched an investigation and is intent on questioning U.S. officials about the unemployed car salesman's claim that he was wrongly targeted as an Islamic militant. Masri's story, if true, would offer a rare firsthand look at one man's disappearance into a hidden dimension of the Bush administration's war on terrorism. Since the Sept. 11 attacks, U.S. authorities have used overseas detention centers and jails to hold or interrogate suspected terrorists, such as at Guantanamo Bay, Cuba. Many of the estimated 9,000 prisoners in U.S. military custody were captured in Iraq, but others, like Masri, were allegedly picked up in another country and delivered to U.S. authorities in Afghanistan or elsewhere for months of confinement.