Hungarian police said on Thursday they have launched a criminal investigation into one of the country’s worst boat accidents that left seven South Korean tourists dead and 21 others missing.

A sightseeing boat sank in driving rain on the Danube river near the parliament building in Budapest after a collision with a larger cruise boat on Wednesday evening, officials and media reports said.

Army divers joined police in the hunt for survivors, which continued through the night.

The search operation has been extended the length of the Danube in Hungary, officials said, as weeks of heavy rainfall has led to high water levels and a fast-moving current, complicating rescue efforts.

Local media reported that one body was found several kilometres south of the site of the sinking, although this was not confirmed by the emergency services.

A total of 33 South Koreans including 30 tourists and three guides were on board the Mermaid, Seoul’s foreign ministry said, confirming the seven dead were Korean.

The youngest on board was a six-year-old girl, travel agency officials said.

The 26m boat was also carrying two Hungarian crew members when it went down at 9:15pm (1915 GMT).

‘All possible help’

Emergency services spokesman Pal Gyorfi said in addition to the seven dead, another seven people were taken to hospital with symptoms of hypothermia and shock.

Police spokesman Kristof Gal confirmed that a further 21 were missing.

“The government expresses its condolences to the families of the South Korean victims of the Danube boat accident,” the Hungarian government said on its Facebook page.

“The government is providing all possible help to the police, emergency services, divers, ambulance staff and doctors treating the survivors.”

South Korean Foreign Minister Kang Kyung-wha was to leave later on Thursday for Budapest as head of a government taskforce, his office said.

A witness told the Index.hu news site that the Mermaid, which could carry up to 60 people, had been hit from behind by a large cruise boat.

Web camera footage from a hotel rooftop posted on local news sites appeared to show the larger vessel colliding with the Mermaid.

Chilly waters

Wreckage was found on the riverbed after several hours of searching near the Margaret Bridge, one of the main links between the two parts of the Hungarian capital, local media said.

Access to the river has been blocked by the authorities, according to public television.

The temperature of the water is chilly, between 10 and 15 degrees Celsius, according to local media.

The boat was regularly serviced and had no apparent technical faults, Mihaly Toth, a spokesman for its owner Panorama Deck, told Hungarian news agency MTI.

“We know nothing about how it happened, the authorities are investigating, all we know is that it sank quickly,” said Toth

During the night search, a film crew working from a bridge south of the accident site used reflector lights to help light up the water through the gloom and pouring rain, local media reported.

The accident happened on a popular part of the Danube river for pleasure trips, from where passengers can view the city and parliament building illuminated at night.

Dozens of small sightseeing boats ply the river through Budapest every day. Larger river cruise boats travelling on the Danube between Germany and the Black Sea typically spend several days moored in the capital.

South Korean President Moon Jae-in instructed the government to “deploy all available resources” for the rescue, his office said.

Seoul planned to send a team of 18 officials to assist the authorities in Budapest, South Korea’s Yonhap news agency reported.

Embassy staff have also been assisting the emergency services in the identification of victims.

The Hungarian interior and health ministers visited the scene and expressed condolences to the families of the victims.