A HELICOPTER which crashed in a North Sea gas field last month killing all 11 people on board - including three from the North-East - had a "manufacturing anomaly", it was revealed last night.

The helicopter plunged into the sea 30 miles off Norfolk without warning as it ferried workers between gas rigs.

Among the dead were the pilot, Captain Mark Wake, 42, who was born and brought up at Newton-on-Derwent, near York. Also aboard were Douglas Learwood, of Marton, and Stuart Coggon, from Middlesbrough.

A report yesterday from the Air Accidents Investigation Branch (AAIB) said the problem, which could have led to fatigue, was built into one of the Sikorsky S-76A's main rotor blades, which fractured in the crash on July 16.

It was made worse by a lightning strike in 1999 that damaged the blade's titanium spar, said the report.

But neither the damage nor the manufacturing anomaly were detected during an inspection made by Sikorsky after the lightning incident. The helicopter was repaired and returned to service.

The AAIB said the anomaly would have been hidden from view during routine in-service blade inspections.

* Both pilots and nine passengers died in the crash. Five bodies were recovered on the night of the July 16 accident and five more on July 19. The search for the 11th person was called off on July 30.