Police in the Philippines are looking for three people they want to question -- one man and two women -- in connection with the blast at a crowded market in Davao City that killed 14 people Friday night.

Philippines National Police Chief Ronald dela Rosa told CNN Saturday the blast was caused by an improvised explosive device made of mortar rounds -- a fact that made it likely that extremist groups being behind the deadly explosion.

Dela Rosa told reporters at a news conference in the southern Philippines city Saturday evening that authorities had eight witnesses, and a sketch of one suspect.

Sixty-eight people were injured in the explosion at the crowded night market in President Rodrigo Duterte's hometown, Dela Rosa said. Fifteen of the injured are in critical condition, CNN Philippines reported, citing Southern Philippines Medical Center director Leopoldo Vega.