At least 32 people have died after a ferry with hundreds of people on board sank near the central Philippine port of Cebu.
"About 170 of the 831 passengers are still missing but we expect the number of missing to decrease and the casualties to increase," Transportation Secretary Joseph Emilio Abaya told Reuters news agency.
The ferry sank on Friday after colliding with a cargo vessel.
Many of the survivors were sick from swallowing oil and seawater, disaster officials said.
Passenger Jerwin Agudong told radio station DZBB that some people were trapped and he saw bodies in the water.
"It seems some were not able to get out. I pity the children. We saw dead bodies on the side, and some being rescued," he said.
The passenger said the crew of the ferry distributed life jackets while the ship was slowly sinking.
The captain of the ferry MV Thomas Aquinas ordered the ship abandoned after it began listing and then sank after hitting the cargo vessel, coastguard officer Joy Villegas said.
Accidents at sea are common in the Philippine archipelago because of frequent storms, badly maintained boats and weak enforcement of safety regulations.
In 1987, the ferry Dona Paz sank after colliding with a fuel tanker in the Philippines, killing more than 4,000 people in the world's worst peacetime maritime disaster.
In 2008, the ferry MV Princess of the Stars capsised during a typhoon in the central Philippines, killing nearly 800 people.