Philippine troops defused a powerful bomb found in a packed bus in a southern town on Monday, after the US Embassy warned that terrorists might carry out attacks in bus terminals, officials said Monday. The bomb - black powder stuffed in a pitcher with steel fragments for deadlier effect - was hidden in a backpack on a bus where it was hastily abandoned by two men late Sunday in southern Maguindanao's Talitay town, regional army spokesman Lt. Col. Julieto Ando said. Panicking passengers grabbed the bag and hurled it outside the bus. Police and army experts later defused the bomb, which was attached to a timer and batteries but was not yet set to explode, Ando said. A police investigation was under way to determine whether the foiled bombing was planned by al-Qaida-linked operatives, or linked to lingering political wrangling following May 14 congressional and local elections, he said.