Dutch police are trying to solve the mystery of how a North-East woman fell overboard from a ferry.

The 40-year-old woman, from the Gosforth area of Newcastle, fell over a barrier on the ship's top deck and, watched by her horrified male friend, plunged 60ft into the North Sea.

A search and rescue operation was called off after seven hours, amid mounting speculation that the woman, who has not been named, would not be found alive.

Officers from Amsterdam Police were yesterday on board the DFDS vessel the Queen of Scandinavia in a bid to find out how she fell.

The accident happened at around 2.25am yesterday, about 55 miles from the coast of Cromer in Norfolk. The ship had left North Shields at 5.30pm on Tuesday night, bound for the port of Ijmuiden, near Amsterdam, Holland.

A frantic search by a host of rescue vehicles was called off at 10am. Roland McKie, watch manager at Yarmouth Coastguard, which co-ordinated the search, said: "Sadly, after seven-and-a-half hours, we were unable to find any signs of the woman.

"The search has now been terminated since it is now well beyond the expected survival time, given the water temperatures."

A spokeswoman for the ferry operator, DFDS, said: "The search has been called off. No one could survive more than six hours in the North Sea, even at summer temperatures of about 17 degrees, as it was today."

The 35,000-tonne ship, carrying 800 passengers, stopped as soon as the alarm was raised, but took around 15 minutes to slow from its speed of 20 knots and return to the spot where the woman fell.

A man-overboard marker buoy was dropped straight after the woman fell and a lifeboat launched from the ferry within five minutes. Rescuers later spotted the buoy, but the woman was not found.

The search and rescue operation included an RAF helicopter and four boats - the Queen of Scandinavia with its fast rescue craft, plus the Rassay, which services the nearby Viking Field of gas platforms, along with its fast rescue ship.

The ferry had been due to dock at Ijmuiden at 3pm yesterday afternoon, but was expected to arrive at 9.30pm last night. It will return to Tyneside later on today.

Norfolk Police were yesterday liasing with Northumbria Police to trace the missing woman's relatives.