A homemade bomb killed two men when it exploded Thursday on the motorcycle they were riding in a southern town, police said. A bystander was wounded.
Investigators were trying to determine whether the men were innocent victims or were carrying the bomb that went off accidentally in Maguindanao province's Datu Odin Sinsuat township, provincial police chief Senior Superintendent Marcelo Pintac said.
An earlier report said the bomb was fashioned from a mortar round, but Pintac said a bomb squad was still trying to reconstruct the device from debris recovered at the scene.
Pintac said the bomb exploded as the men were passing the home of a provincial official who was killed in a car bombing several months ago.
Authorities have blamed previous bombings in the region on Muslim rebels, militants, rival politicians and extortion gangs.
(This version CORRECTS that 2 were killed, 1 wounded)