MANILA - The Philippines ordered troops and police on heightened alert Sunday after a restaurant attack killed six in its restive southern region, but said there were no clues yet to the culprits.
Interior Secretary Mar Roxas said investigators were reconstructing the bomb site to gather more clues on Friday night's attack in Cagayan de Oro, a relatively peaceful city in Mindanao island, where various rebel groups and armed gangs operate.
"We are doing everything (to determine the suspects). We have placed the police in Mindanao, the intelligence community and the army on heightened alert to prevent a similar attack," Roxas said over DZBB radio.
Investigators have yet to determine the explosive used in the attack, which hit a bistro packed with at least 100 people. Most were doctors and pharmaceutical representatives who had just attended a national convention at a nearby hotel.
Forty-eight others were wounded in the blast, police said.
Contrary to earlier reports, Roxas said investigators had not found shrapnel or metal fragments at the blast site, which would have indicated an explosive device made from a mortar bomb.
"According to the doctors who did the autopsy report, there were no shrapnel that can be attributed to a grenade explosion," Roxas said.
"It is also not an IED (improvised explosive device) made from mortar or artillery shell," he said.
Ordnance experts have found wires and a battery that could have been used as a trigger but not much else.
Roxas's statement suggested the attack may not have been the work of Muslim militants who operate in other parts of the south and are known to use mortar bombs rigged to a timing device.
Asked whether investigators were looking at any specific group behind the blast and what the motive could be, he said: "If it's business rivalry, fighting over land, or terrorism we could not say yet until we know all the facts and details."
Cagayan de Oro is a bustling city that has been relatively unscathed by a decades-old Muslim and communist insurgency that have plagued parts of the south in this largely Catholic country.
The Moro Islamic Liberation Front (MILF), the country's largest Muslim insurgent force, said Sunday said it had no forces operating near Cagayan de Oro and condemned the attack as un-Islamic.
The MILF, which is negotiating a peace deal with Manila, was also willing to help track down the perpetrators if asked by the government, said the group's vice chairman for political affairs Ghazali Jaafar.
"We have an existing agreement to help each other out in interdicting criminal elements," Jaafar told AFP.