A diver prepares to dive to the wreckage under Margaret Bridge in Budapest, Hungary, May 31, 2019. Seven people are confirmed dead and seven have been rescued, while 21 people remain missing in the waters. A South Korean group on a package tour of Europe — including 30 tourists, two guides and a photographer— were on an hour-long sightseeing tour of Budapest when their boat collided with a Viking cruise ship during a downpour Wednesday evening. (AP Photo/Laszlo Balogh)
A diver prepares to dive to the wreckage under Margaret Bridge in Budapest, Hungary, May 31, 2019.

Rescue crews in Budapest Friday are working to raise a sightseeing boat from the bottom of the Danube River, while searching for 21 people still missing after a cruise ship collided with the smaller tour boat late Wednesday.

Seven people are confirmed dead and seven have been rescued All but two people on the boat were South Korean tourists.

Hungary's state TV reported that all rescued people have been released from the hospital except one who is being treated for broken ribs.

Hungarian police arrested the Ukrainian captain of the Viking cruise ship, identifying him as Yuriy C.

Police say he is suspected of "endangering waterborne traffic resulting in multiple deaths."

Two women watch a rescue vessel off the Margit bridge on the Danube river where a sightseeing boat had capsized in Budapest, Hungary, May 31, 2019. Hungarian police have detained the captain of a cruise ship that collided with a sightseeing boat packed with South Korean tourists, causing it to sink quickly in the Danube River, as loved ones of the missing and dead were expected to arrive Friday in Budapest. (AP Photo/Marko Drobnjakovic)
Two women watch a rescue vessel off the Margit bridge on the Danube river where a sightseeing boat had capsized in Budapest.

​​Investigators say the Viking ship and the tour boat, Mermaid, were sailing side-by-side on the Danube in central Budapest when both vessels arrived at pillars under the Margit Bridge.

The Mermaid turned in front of the Viking ship which struck the boat and capsized it. Police say the Mermaid sank in just seven seconds, giving passengers and two Hungarian crew members almost no time to get to safety.

Hungarian rescuers say heavy rain and the Danube's strong currents are hampering their efforts. They have extended their search downriver into Serbia.

Hungary’s Prime Minister Viktor Orban said the boat accident was "shocking," and asked authorities to conduct a thorough investigation into the accident.

South Korean President Moon Jae-in has sent a delegation of Korean officials and experts to Budapest to help.