Philippine police say at least nine people were killed Tuesday and more than 20 others wounded when a powerful blast ripped through a commuter bus in the southern Philippines.
Officials say the explosion occurred as a bus operated by the Rural Transit company passed a university in the town of Maramag on the strife-torn island of Mindanao.
The blast sent shrapnel and debris flying through the vehicle. Many of the victims were students.
Investigators are trying to determine the motive for the blast.
Muslim extremists and extortion gangs have been blamed for bus bombings in the southern Philippines in the past. Buses operated by the Rural Transit company have been targeted in some of the attacks.