At least 12 people were reported missing after a tourist boat capsized on a popular river in central Vietnam, officials said Sunday.The accident occurred around 9 pm Saturday (1400 GMT), when a leisure vessel carrying about 50 passengers on the Han River in the city of Da Nang city capsized, Major General Ngo Quy Duc, deputy commander of Military Region 5, said.As of 1 am Sunday, rescue forces have rescued 32 people, he said, adding it was impossible to confirm the exact number of those still missing.At least one foreigner was reported travelling on the boat, the online newspaper Vnexpress reported from the scene.Vietnamese Prime Minister Nguyen Xuan Phuc ordered local authorities to quickly search for the missing.Hot weather had prompted many passengers to climb up to the deck, putting the boat off balance and causing it to overturn, the Tuoi Tre newspaper said.Rescue forces are using fishing nets to prevent victims from being swept further, according to city official Tran Duc Tho.