Philippine rescuers searched the smoldering ruins of a burnt-out ferry on Thursday for any survivors or more victims of a fire that swept though the inter-island vessel killing 29 people, including a 6-month-old baby, authorities said.

Investigators have yet to identify the cause of the fire that started at about 11 p.m. (1500 GMT) on Wednesday off the southern island of Basilan, when many passengers were asleep in air-conditioned cabins on the ferry's lower deck.