BERLIN (AP) — Two cargo ships collided in the North Sea off the coast of Germany on Tuesday and one of them sank, German authorities said. At least one sailor died and rescuers were trying to find another four.

The vessels collided shortly before 5 a.m. about 22 kilometers (14 miles) southwest of the island of Helgoland, Germany's Central Command for Maritime Emergencies said. The site of the collision was about 31 kilometers (19 miles) northeast of Langeoog island, which is just off the German mainland.

The British-flagged Verity, which had seven people on board and was en route from Bremen, Germany, to the English port of Immingham, sank shortly after the collision. A signal from the ship was lost at about 5:20 a.m., suggesting that it had already gone down, and wreckage was found.

Two sailors were rescued and taken to a hospital, where they weren't in a life-threatening condition. The body of one man was recovered, while four other people were still missing.

“We are now doing everything humanly possible to rescue more people alive,” the head of the emergency command, Robby Renner, said at a news conference in Cuxhaven.

The water temperature at the time of the collision was about 12 C (54 F), which experience shows that people can survive for about 20 hours, said Michael Ippich of the German Maritime Search and Rescue Service.

Several rescue ships and aircraft taking part in the search hadn't located the missing crew members by late afternoon. Rescuers considered the possibility that they were still inside the Verity and sent divers down to the wreck at a depth of about 30 meters (around 100 meters) to check whether there were any signs of life.

But the divers were unable to find anything, and increasingly strong currents meant that they couldn't immediately try again. Visibility at the site was low and any dives could only be made in a short window between tides.

The Verity was 91 meters (299 feet) long and 14 meters (46 feet) wide. It was carrying steel coils, according to Renner.

The other, bigger ship — the Bahamas-flagged Polesie — remained afloat and had 22 people on board. None of them was believed to be injured. The vessel was heading from Hamburg to A Coruña, Spain. The Polesie is 190 meters (623 feet) long and 29 meters (95 feet) wide.

There was no immediate word on the cause of the collision.

Vessels supporting the rescue effort included a cruise ship, the Iona, that was en route from Hamburg to Rotterdam and had doctors on board.