Two cargo ships crashed into each other in the North Sea, with a search currently ongoing for survivors.
One body has been recovered and another two people have been rescued, while four crew members remain missing.
German authorities said one rescued man was taken to a hospital on land and the other was on his way to hospital on board a maritime rescue cruiser.
The ships, Polesie and Verity, collided in the early morning about 14 nautical miles south-west of the island of Helgoland, Germany’s Central Command for Maritime Emergencies said.
The British-flagged Verity, apparently sank with seven people onboard, while the Polesie remains waterborne with its 22 passengers.
The search operation currently includes a rescue cruiser, police boats, sensor aircraft and a helicopter among other vessels.
The emergency command said the 300ft British ship was headed from Bremen, Germany, to the English port of Immingham.
Robby Renner, Germany’s head of Central Command for Maritime Emergencies, told a news conference in Cuxhaven it is possible the remaining crew are still alive inside the sunken vessel and that his team is doing “everything humanly possible” to rescue them.
Michael Ippich, of the German Maritime Search and Rescue Service, said the water temperature at the time of collision was 12C (54F), which people can survive for about 20 hours.
Mr Ippich told reporters: “The conditions on the spot are extremely difficult.
“Because of the weather and visibility, it’s incredibly difficult to conduct such an operation.”
The P&O cruise ship Iona is among those that have joined the search, alongside the rescue cruisers ‘Hermann Marwede’ and ‘Bernhard Gruben’.
It is said to have doctors on board who are able to treat people if needed, while more medical personnel are being taken to the scene by helicopter.
A spokesperson for P&O Cruises said: “P&O Cruises Iona is currently involved in a search and rescue operation off the coast of Germany.
“The incident is ongoing and Iona’s cooperation complies with international maritime law as well as being consistent with the company’s moral and legal obligations.
“Iona is scheduled to be at sea today and this event should have no impact upon tomorrow’s scheduled call to Rotterdam or the onward itinerary.”
Faversham Ships Ltd, which owns the Verity, described the incident as “ongoing” and said it was working with local authorities.
A spokesman for Associated British Ports, which owns the port of Immingham, confirmed it was due to arrive there.