The captain of a vessel that collided with a tour boat on the Danube river in Budapest, resulting in at least seven deaths, has been arrested, police say.
The 64-year-old Ukrainian national was held as a suspect over reckless misconduct in waterborne traffic leading to mass casualties.
The boat carrying South Korean tourists sank seven seconds after the collision during a rainstorm on Wednesday.
Hopes have faded that any of the 21 people missing will be found alive.
A criminal investigation has been launched into the collision, a rare incident on the Danube where navigation is busy but generally safe.
Seven people rescued alive were suffering from hypothermia but stable, an ambulance spokesman said.
Witness saw people 'screaming in the water'
CCTV footage showed the boat that sank - Hableany, or Mermaid - being hit from behind by a larger tour boat - Viking Sigyn - near the Margit (Margaret) Bridge in central Budapest after 21:00 local time (19:00 GMT).
"The whole thing happened very quickly" said Clay Findley, a US tourist who was on the Viking Sigyn.
"I thought at first we were going to miss it, but the front of the Viking hit the back of that little boat... and then the hull popped up on the opposite side of the ship, just a few seconds later, and then it was down."
Another passenger, 66-year-old Ginger Brinton from the US, told the AFP news agency that he was on the boat's balcony when he "saw people in the water, screaming for help".
He added: "We never felt any bump. We didn't realise. We just saw people in the water. It was just terrible."
No-one on the Swiss-registered Viking Sigyn was injured.
Hungarian police said the investigation yielded evidence that raised questions of personal responsibility so it questioned the captain - identified as Yuriy C., from Odessa - as a suspect and later decided to take him into custody.
Emergency crews found the wreckage of the Hableany, a double-decker river cruise boat built in 1949 in the former Soviet Union, on the riverbed near the Margaret Bridge and were preparing to lift it.
What is known about the rescue operation?
Thirty South Korean tourists and three tour guides, as well as two Hungarian crew, were on board the Hableany.