( dpa ) - Philippine police said Thursday they suspect that an extortion syndicate was behind a bomb attack on a tuna canning factory in a southern city, which killed four people and injured 30.
The explosion at the Philbest Canning Company in General Santos City, 1,065 kilometres south of Manila, occurred Wednesday evening as workers were changing shift.
Chief Superintendent Felizario Serapio, a regional police director, said investigators were looking into the possible involvement of the al-Khobar group, which has been extorting money from businessmen and bus companies.
"While the management denied receiving threats prior to the blast, we know that the al-Khobar has been extorting money from traders in the area," he said. "We are looking into the group's involvement in Wednesday's bombing."
Serapio said investigators were also checking if there were labour disputes at the company that could have prompted the attack.
Initial investigation showed that an improvised explosive device was planted in a motorcycle parked in front of the factory's gate. The bomb went off as workers were going home and a new shift was taking over operations.
Serapio said police were not yet discounting the involvement of terrorists in the bombing, although he noted that "if this was a work of terrorists, then they should have planted the explosive at the heart of the city."
"The incident happened about eight kilometres from the city proper," he added.
General Santos, tagged as the tuna capital of the Philippines, has been hit by terrorist bombings in the past. The attacks were blamed on such al-Qaeda-linked groups as the Abu Sayyaf and the Jemaah Islamiyah.