Manila - Divers from two salvage firms began to retrieve toxic chemicals from a sunken passenger ferry in the Philippines Tuesday, a senior official said.

Transportation Undersecretary Elena Bautista said about 400 packs of hazardous pesticide endosulfan was retrieved from Princess of the Stars, which sank off central island of Sibuyan, 300 kilometres south of Manila.

The passenger ferry was carrying more than 800 people and at least 10 tons of endosulfan when it capsized in June after it was battered by strong winds and huge waves at the height of a typhoon.

Aside from endosulfan, salvage divers hope to retrieve four other toxic chemicals, although in smaller volumes, stuck in the cargo bay of the ferry.

Some 100,000 litres of bunker fuel stuck in the ship's fuel tank will also need to be retrieved.

"If the weather is good, the retrieval operations will be completed within 12 to 16 days," Bautista said.

The Philippine coast guard barred on Monday all fishing activities within 1 kilometre around the site of the sunken ferry to ensure the salvage operations would be unhampered.

Bautista said that after removing the toxic chemicals, the divers would start retrieving dead bodies still trapped inside the ferry. Only about 200 bodies of the 800-plus passengers were recovered after the accident.

The sinking of the Princess of the Stars was one of the worst ferry disasters in the Philippines, the site of the world's worst peacetime shipping accident when a passenger ferry collided with an oil tanker in 1987, killing more than 4,000 people. (dpa)