A boat carrying dozens of tourists capsized in Vietnam’s Ha Long Bay on Saturday, leaving at least 34 people dead, according to state-owned media.

The boat, carrying 48 passengers and five crew members, was on a sightseeing tour when a sudden thunderstorm with strong winds created high swells that overturned it, Vietnamese news outlets reported.

Rescue teams that included naval commandos from the Quang Ninh Province, in northeastern Vietnam, recovered 34 bodies, with at least eight children among the dead, according to Dantri, a state-owned media outlet.

The emergency crews, working past nightfall, had pulled at least 10 survivors out of the water, state media reported. Among those rescued was a boy who had been in the water for several hours.

“It’s the worst accident I’ve known in Ha Long Bay in the last 25 years,” Bui Cong Hoan, deputy chairman of Ha Long Tourist Boat Association, said by telephone.

All of the passengers and crew members were Vietnamese citizens, state-run media said. Images of the incident showed the boat completely overturned, its hull sticking out above the water.

Vietnamese media reported that of one family, with two parents and two children, only the mother had survived.

Pham Minh Chinh, the prime minister of Vietnam, ordered civil defense workers and the Defense and Public Security Ministries to support the search efforts, Vietnam’s official government news site said.

The boat was returning from a tour of Dau Go and other limestone caves in Ha Long Bay, a UNESCO World Heritage Site with more than 1,600 islands, when the storm broke out, Mr. Hoan said. The boat, part of a tour association, was among hundreds of vessels that ferry tourists around the bay each day.

In 2022, 17 tourists died when a speedboat capsized in the waters off Quang Nam in southern Vietnam. The boat’s captain, was sentenced to seven years in prison, according to Vietnamese news outlets.

In 2009, 40 people were killed when an overloaded ferry sank in a river in central Vietnam, in what the police described as one of the country’s worst such disasters.