MANILA, December 29, 2009 (AFP) - The death toll from a ferry disaster in the Philippines could be much higher than first thought, with dozens of passengers believed to have been left off the official manifest, the coast guard said Tuesday.

As many as 44 people remain missing after the MV Baleno-9 sank in deep waters on Saturday, even though the passenger list indicates only 10 people should be unaccounted for, said coast guard commander Gil Villamaria.

The drive-on ferry, which went down in rough seas near Batangas city off the Philippines' main Luzon island's south coast, was listed as having 88 people on board, of which six have been found dead and 72 were rescued.

However Villamaria, an officer at the coast guard centre working on the MV Baleno-9 search, said many people had since come forward saying their relatives were on the ferry but were not listed.

"A lot of people are claiming their relatives were on board. So we list them as missing but they are not in the manifest," Villamaria told AFP.

He said it was possible that those people were mistaken about their relatives being on the sunken ship.

"(But) we are taking their word for it. We don't take chances so we treat it like they were really on board and we consider them as missing also."

It is a common practice in the Philippines for ships' manifests not to include everyone on board.

Many people board the vessels at the last minute or sneak onto the ships without paying, while some companies do not list everyone so they can circumvent laws restricting the number of passengers.

The wreck of the MV Baleno-9 lies in about 350 metres (1,148 feet) of water, beyond the reach of coast guard divers, and special equipment will be needed to reach it to see if there are any bodies trapped inside, said Villamaria.

The sinking of the MV Baleno-9 came just three days after another ferry, the wooden-hulled Catalyn B collided with a fishing vessel and sank in Manila Bay on Christmas Eve, leaving four dead and 23 missing, according to the manifest.

Maritime disasters occur frequently in the Philippines and usually involve poorly maintained, overloaded ferries that form the backbone of travel between the archipelago's roughly 7,000 islands.

Christmas is a particularly dangerous time because millions of people in the Catholic nation travel to be with their families over the festive period.