A wounded worker lies on a hospital bed in General Santos city, southern Philippines, Jan. 30, 2008. (Xinhua/Reuters Photo) Photo Gallery>>>

    MANILA, Jan. 30 (Xinhua) -- Three people were killed while some 20 others were hurt in a blast that rocked a tuna canning facility in the Philippines' southern city of General Santos on Wednesday night.

    The blast took place at past 6 p.m. local time (1000 GMT) at a Philbest Canning factory, Philippine TV network ABS-CBN reported.

    The victims were mostly employees of the factory who were going home while another shift was coming in.

    Police said the explosion may have been caused by an improvised explosive device attached on a motorcycle just outside the factory.

    No one claimed responsibility for the blast.

    The police were investigating whether it was an extortion attempt or labor-related incident, said Robert Po, the police chief in General Santos city. He said he was not ruling out an attack by some anti-government radicals.

    General Santos, known as "the Tuna Capital of the Philippines," is a port city located in the southernmost part of the country with most of the country's major tuna canneries.