DA NANG, Vietnam - Tourists are said to be missing after a cruise ship carrying around 50 passengers overturned on the Han River in the Vietnamese city of Da Nang, according to reports.

The incident happened at about 9pm on June 4, 2016, said the VnExpress website.

Over 30 passengers have been taken to hospital, the site said. It reported Vice-General Ngo Quy Duc as saying that 32 people had been rescued.

"The cruise might have had more than 40 passengers. Four missing persons have been identified," he said.

Passengers were reported to be from Vietnam, Malaysia and Korea, among other places. All hotels in Da Nang are said to be checking for missing guests.

The search and rescue area spans 2km from Thuan Phuoc Bridge to the Han River swing bridge, said VnExpress. Fishing boats have been borrowed for search and rescue operations. It is said that 21 passengers are from the same family.

More than 20 divers and police are searching for victims.

The sunken cruise is called Thao Van, said VnEXpress, and had a seating capacity of 28. It was last inspected on May 19, said the site, with the next inspection scheduled for Nov 20.

Ms Dang Thi Xuan, who was crying by the river, said she was a relative of a Nguyen Thi Huyen, of the 21-member family onboard.

She told VnExpress that two of her children, one aged four and the other aged seven, are missing.