At least 12 people, many of them foreign tourists, have drowned after a tour boat sank in Halong Bay in north-east Vietnam, BBC reports. The wooden boat was touring in the Unesco World Heritage Site, in Quang Ninh province, when it went down. Fifteen people, including nine foreigners, have been rescued. It is not yet clear why the boat sank, although a local government official said initial information suggested part of the boat had broken without warning.