Rescue workers were searching a vast length of the River Danube on Thursday for 21 tourists and crew missing after a sightseeing boat collided with a larger ship and sank within seconds.
The captain of a passenger crusier which collided with another boat carrying South Korean tourists which then sank has denied breaking any rules or committing a crime, his lawyer has said.
Police in Hungary have detained the 64-year-old Ukrainian following the collision on the River Danube in Budapest on Wednesday evening that left at least seven people confirmed dead and 21 missing.
The group was on an hour-long sightseeing tour of Budapest when their boat collided with the Viking cruise ship during a storm.
In a statement, the captain's lawyer said treating him as a suspect was "premature" and based on nothing "more than a theory".
Rescue crews on Friday geared up to raise their sightseeing boat from the bottom of the river while scouring the waters for victims.
Hungary's state TV reported that all those rescued have been released from the hospital except one who is being treated for broken ribs.
Officials said preparations to bring up the 70-year-old boat, which was built in the former Soviet Union, could take days.
It was cruising on the river when it collided with a larger passenger boat during a torrential downpour at 22.00 CEST on Wednesday.
"I wouldn't say there is no hope, rather that there is a minimal chance (of finding survivors)," Pal Gyorfi, a spokesman for the Hungarian national ambulance service, told the M1 state broadcaster on Thursday.
"This is not just because of the water temperature, but (also) the strong currents in the river, the vapor above the water surface, as well as the clothes worn by the people who fell in," he added.
Police said a criminal investigation was underway to determine the cause of the accident.
The sunken boat was located near the Margit Bridge, not far from Hungary's neo-Gothic riverside parliament building.
But rescue operations were hampered by the rain and the fast flow of the rising river.
The search for the missing had extended far downstream, even into Serbia, where the Danube flows after leaving Hungary.
Employees from the South Korean Embassy in Budapest were assisting Hungarian officials in identifying those rescued and the victims.
South Korean President Moon Jae-in also dispatched a government task force led by Foreign Minister Kang Kyung-wha.
The boat that sank was identified as the Hableany (Mermaid). Mihaly Toth, a spokesman for owners, the Panorama Deck boating company, said the vessel was on a "routine city sightseeing trip" when the accident happened.