Hopes are fading of finding any more survivors from a boat accident on the River Danube in Hungary in which seven people died.
21 people are still missing two days after the tragedy in Budapest, most of them South Korean tourists.
Police and army boats continued search operations for a second night but their work has been hampered by high river levels and a strong current after weeks of heavy rainfall.
The Mermaid sightseeing boat overturned after colliding with a much larger river cruise ship on a busy stretch of the Danube on Wednesday evening.
At least seven South Korean tourists were killed and 21 people remain missing, including the boat's captain and a crew member, both Hungarian.
Only seven people are known to have survived so far.
Police said the captain of the larger ship, the 135-metre four-storey Viking Sigyn, had been taken into custody and "questioned as a suspect ... in relation to 'endangering waterborne traffic resulting in multiple deaths'."
"After being questioned, 64-year-old Yuriy C, a resident of Odessa in Ukraine, was detained and a request for his arrest has been made," a statement said.
Police have also launched an investigation into possible "criminal negligence on public waterways".
The captain denies having broken any rules or committing a criminal office, his lawyer said in a statement quoted by Hungarian state news agency MTI.
Families of some of the victims are due to fly to Budapest today.
South Korea's Foreign Minister Kang Kyung-wha is also in the city to meet her Hungarian counterpart Peter Szijjarto.
A floating crane was erected near the accident site, as well as a small pier for use by divers.
However, experts warned that the Danube's high current level would make any diving attempts very risky and that lifting the wreck could take several days.
The water level is not expected to start receding before Tuesday at the earliest.
Yesterday police revealed the strong current had swept one of the victims around 11km downstream of the accident site.
The search operation has been extended to cover the entire length of the Danube in Hungary south of Budapest and Hungarian authorities have also contacted their counterparts in neighbouring Serbia.
Lee Sang-moo, chief operating officer of Very Good Tour which organised the trip for the South Koreans, said most of the passengers were in their 50s and 60s, with the oldest a man in his early 70s.
A six-year-old girl who was travelling with her mother and grandparents is also among those missing.
A candlelit vigil for the victims is expected to be held at the South Korean embassy in Budapest this evening.
Yesterday locals laid flowers and lit candles at the embassy and on Budapest's Margaret Bridge near the scene of the tragedy.
