Chief accident investigator Arnie Santiago told reporters: "The way the ship tilted indicates that the cargo moved."

He said the sinking was unusually rapid, and some of the ship's water seals may have been damaged by a fire last year. Passengers and crew said it sank in less than an hour.

David Willis: Passengers awoke to find water pouring in on them

The boat, the Princess of the Orient, had been rocked by strong waves before it sank but should have been able to withstand much worse weather.

Carlos Go, head of Sulpicio Lines, owner of the ship, insisted the ship was in seaworthy condition.

A storm warning prohibited ships of less than 500 tons from sailing but did not apply to the 13,734-ton ferry.

The area where it sank, about 60 miles from Manila, is hit by more than 20 storms of similar magnitude each year.

So far, more than 300 survivors are believed to have been found but at least 50 bodies have been found and 50 more passengers and crew are missing.

Most of the survivors were in shock

Many passengers were asleep when the emergency began and alleged that the crew had failed to give orders to abandon ship.

One survivor said: "We listed, water poured in like a flood, the captain could not control the ship and we went slowly down".

Many of the survivors floated for hours wearing life jackets before they were picked up by local boats. Many were covered in oil from the ship's fuel tanks.

Other survivors, picked up in a flotilla of boats, said they had been lashed by waves as high as six metres as they jumped off the listing vessel.

The ferry - which was authorised to carry 3,000 people - was on its way to the central Philippine island of Cebu.

Widespread flooding

Residents resort to rafts in Malabon near Manila

The storm which battered the ferry has also resulted in widespread flooding.

Hundreds of thousands of people have been evacuated from flooded villages around the capital, Manila, and the northern island of Luzon, where the floods also killed at least 20 people.

President Joseph Estrada has declared a state of calamity in the northern provinces of Pampanga and Pangasinan.

History of disaster

The Philippines depends on ferries to link its 7,000 islands together.

Though its record has been improving, the Philippines has a history of shipping disasters.