They are undergoing treatment at Sandig Hospital in Tacurong City.
Injured were Analyn, Nilda and John, all surnamed Lorenzo, and Anthony Gonio.
Tacurong City police investigators said the bomb exploded five minutes after it was left by a lone suspect at the baggage counter of the Kimsan Department Store.
Police said the improvised bomb was made up of a small sealed container with explosive powder inside, and attached to a contraption of batteries and a cell phone. — Ramil Bajo, James Mananghaya