The captain of a cruise boat in Hungary that collided with a smaller tour vessel, killing seven people, has been arrested.
Seven people were rescued, Hungarian officials said, but 21 were still missing.
Police said the Ukrainian captain, 64, is suspected of endangering water transport and was arrested after questioning.
In line with Hungarian laws, the suspect was identified only as Yuriy C, from Odessa.
The boats collided during an evening downpour on Wednesday, sinking the smaller vessel.
Nineteen tourists and two Hungarian crew members are still missing from the accident on the Danube River.The sunk boat had 35 people on board, including 33 South Koreans.
Searches are continuing with more than 200 divers, but there is little hope of finding more survivors, a spokesman for the national ambulance service said.
The South Korea-based Very Good Tour agency, which organised the trip, said the boat was on its way back after an hour-long night journey when the accident happened.
The group consisted of 30 tourists, two guides and a photographer, and the cruise was part of a package tour of Europe.
Pal Gyorfi, a spokesman for the National Ambulance Service, said those rescued were in hospital in stable conditions.
By Thursday, Mr Gyorfi said there was little chance of finding more survivors.
"As an ambulance spokesman I am not inclined to say there is no hope, so I would rather say there is a minimal chance," he said.
The sunken boat was found early on Thursday near the Margit Bridge, not far from the neo-Gothic Parliament building on the riverbank.
Officials said searchers were checking the Danube kilometres downriver. The river was fast-flowing and rising with the heavy rain. Water temperature was about 11°C.
Earlier, the news website Index.hu said one of those rescued was found near the Petofi Bridge, which is about 3 kilometres south of the parliament building.
Dozens of rescue personnel, including staff from the military, were involved in the search.
Employees from the South Korean embassy in Budapest were assisting Hungarian officials in identifying those rescued and the dead.
South Korean President Moon Jae-in has called Hungarian Prime Minister Viktor Orban to discuss rescue operations.
The presidency in Seoul said on Thursday that Mr Moon thanked Mr Orban for his government's rescue efforts and requested further support to find the missing, treat survivors and recover bodies.
The South Korean Foreign Minister, Kang Kyung-wha, and a team of officials left for Hungary on Thursday to assist with the rescue operations and support passengers and their families.
The Very Good Tour agency said the tourists left South Korea on May 25 and were supposed to return on June 1.
Most of them were family groups and they included a girl, 6, whose name did not appear on a list of survivors provided by the agency.
Senior agency official Lee Sang-moo the seven rescued South Koreans were six women and one man aged between 31 and 66.
The company is arranging for family members of the tourists to travel to Hungary as soon as possible.
The boat that sank was the Hableany (Mermaid), which was one of the smallest vessels in the sightseeing company's fleet.
It had two decks and a capacity for 60 people, or 45 for sightseeing cruises.
Mihaly Toth, a spokesman for the Panorama Deck boating company, said the Hableany was on a "routine city sightseeing trip" when the accident happened.