BUDAPEST -- The Ukrainian captain of a large hotel ship that collided with a small tourist sightseeing boat in central Budapest Wednesday has been detained after being questioned as a suspect, Hungarian police said here on Thursday.

"In order to clarify the circumstances of the accident, the Budapest Police ordered an investigation involving a nautical expert. Investigators held an inspection and seized material evidence," the police said in a statement published late Thursday evening.

"On the basis of the personal and material evidence obtained during the investigation, there was a well-founded suspicion on the person, so the Ukrainian captain of the hotel ship was questioned as a suspect by the investigators in relation to threat of waterborne traffic, causing fatal mass disaster," the statement added.

The statement concluded: "After being questioned, 64-year-old Yuriy C., resident of Odessa, was detained and a motion for his arrest has been made."

The sightseeing boat, the "Hableany" (Mermaid in English) carrying 33 South Korean tourists and two Hungarian crew collided with another vessel, a large Swiss hotel boat (type Viking) and sank in the Danube in the evening on Wednesday. At least seven died in the accident.

Hungarian authorities held a press conference Thursday morning and confirmed that 35 people were on board the Hableany, seven people were dead, seven saved, all South-Koreans, and 21 were still missing, including the two Hungarian crew members.

The Mermaid has been found close to the Margit bridge, and preparatory work initiated to hoist the wreckage out of the waters, but the flooding of the Danube slowed down the operation, that might take long days, according to experts.