More than 36 hours after the last contact with the missing Malaysia Airways jet, officials said Sunday they were widening the search to cover the sea around Malaysia and off Vietnam. Malaysia's air force chief Rodzali Daud said military radar showed the missing Boeing 777 jet may have turned back before disappearing, adding that authorities were "trying to make sense of that." International law-enforcement agency Interpol has confirmed on Sunday that at least two passengers on the missing Malaysia Airlines flight used stolen passports that were registered as missing with them, and said it was "examining additional suspect passports." "We have not determined a nexus to terrorism yet, although it’s still very early, and that’s by no means definitive,” one senior U.S. official told NBC News on Saturday. Two names on the passenger manifest matched passports reported stolen in Thailand according to foreign governments and NBC News sources. The plane, carrying 239 people, including three Americans, vanished without sending a distress signal. A Malaysia Airlines representative speaking in Beijing to relatives of passengers of Flight 370 said the airline was fearing the worst.