Manila: The Philippine military is looking at the possibility that insurgents were behind Tuesday’s bus blast in Bukidnon that killed 11 people.

At least 31 passengers were wounded.

Armed Forces of the Philippines (AFP) Spokesperson, Col. Restituto Padilla said they are eyeing the possibility that a Mindanao-based “terror group” had been involved in the bombing of the Rural Transit Mindanao Inc (RTMI) bus.

“We are looking possible involvement of terror groups in the attack,” he said in a press briefing at Camp Emilio Aguinaldo, the military’s headquarters, in suburban Quezon City on Wednesday.

Similar incidents in the past have been blamed on crime syndicates or groups trying to extort money from bus companies plying the Mindanao route.

“Although there had been incidents of extortion carried out on bus companies in Mindanao, it is not conclusive that this is the same motive in this particular case,” Padilla said.

Saying the incident was likely a terrorist act, Padilla did not mention any group that could be responsible for the blast.

According to reports, the RTMI bus was travelling in the village of Mus-wan in Maramag town in Bukidnon when the blast occurred at the front of the vehicle.

The RTMI bus headed for Cagayan de Oro City from Tacurong City and had stopped to pick up students from the Mindanao Central University who flagged down the vehicle, the blast occurred at 12.15pm.

The moment when the bomb exploded had been captured in a closed-circuit television footage.

“The bomb was made from an unexploded mortar shell,” he said adding that such explosives could only come from the military or from a group that had bought or kept them in storage after finding them in the field.

Padilla however admitted that there had been incidents in the past when buses of the RTMI were targeted by extortionists.

“There had been at least two other similar bus bombing incidents in the past involving RTMI,” he said.

Independent tallies show that there have been four incidents targeting RTMI buses over the last four years.

Last November 6, an improvised electronic device detonated inside an RTMI bus no 204 in Maramag, Bukidnon, injuring six people. On August 2012, six people were injured in a blast inside another RTMI bus in Zamboanga City.

But the most devastating blast involving an RTMI bus, with the exception of that last Tuesday, was the October 21, 2010 explosion that occurred on a vehicle travelling in Dalahican village in Matalam, North Cotabato. Ten passengers were killed in the explosion.

Meanwhile, at the Presidential Palace, deputy press secretary Abigal Valte said the government was on top of the situation and that the Philippine National Police was conducting investigations into the incident.

“We condemn this act of violence as we convey our sympathies to the families of the victims,” Valte said.