MANILA, Philippines » Philippine police and army forces have arrested five suspects in a bus bombing that killed 10 people in the country’s south.

The bus was traveling Thursday with 50 passengers when a bomb ripped through the vehicle, wounding nine others in North Cotabato province’s Matalam township.

Lt. Col. Benjamin Hao, an army spokesman, said Sunday that the men were arrested in North Cotabato and Cotabato city. A 15-year-old boy apprehended Friday allegedly acknowledged bringing a bag to the bus not knowing it had a bomb. He implicated four other men who were arrested the next day.

Officials earlier said the blast may have been the handiwork of an extortion gang with links to Muslim militants, but Hao said the suspects’ affiliation was still under investigation.