A sudden monsoon squall overturned a crowded inter-island ferry in the Philippines, drowning at least 40 people, officials said.

Maj. Gen. Jeffrey Sodusta, the regional army commander, said 76 people were rescued and taken to two hospitals for treatment after the Don Dexter Cathlyn was battered by winds and waves shortly after leaving port in central Masbate island for nearby Sorsogon province on Tuesday. He said 40 bodies were recovered, including 11 children.

The ship's manifest listed 119 passengers and a crew of six on board, though ferries frequently carry more people than are officially listed.

Masbate provincial police chief Reuben Sindac told Manila radio station DZBB the ferry was sailing in relatively clear weather until the squall.

Police officer Roy Almine, who helped in the rescue, said huge waves and strong monsoon winds suddenly hit the boat, causing it to overturn and tossing passengers into the sea.

"There was some kind of whirlwind," Sindac said. "There was no rain, no typhoon; the waters were calm when it happened.

"The ferry was not passenger-friendly. There were high railings and tarpaulin on the side so when the vessel overturned, these may have helped to trap the passengers."

Such accidents frequently happen in the Philippine archipelago because of tropical weather, badly maintained passenger boats and weak enforcement of safety regulations.

The typhoon-prone country was the scene of the world's worst peacetime maritime disaster when the ferry Dona Paz sank in 1987, killing more than 4,341 people.

In June, the 23,800-ton Princess of the Stars went belly up during a typhoon close to Romblon province, near Masbate, killing more than 800 people on board.

The discovery of several drums of toxic chemicals held up the retrieval of bodies inside the ship until last week. The chemicals have been removed by marine experts.