More helicopter flights have been grounded after the ditching of a Super Puma in the North Sea on Thursday.
Air accident investigators have found a cracked shaft in the main gearbox of the Bond EC 225 Super Puma helicopter.
Its pilot carried out a controlled landing off the coast of Aberdeen after an oil pressure warning light came on.
Bond said it is continuing its suspension of all EC 225 flights, and has also now grounded its AS332L2 helicopters.
A Bond AS332L2 crashed in the North Sea in 2009. All 16 men on board were killed.
The Air Accidents Investigation Branch said the cracked shaft in the gearbox of the EC 225 that was ditched on Thursday was found near a manufacturing weld.
The crack stopped the helicopter's oil pumps, their report said.
The report said: "The crew of the helicopter carried out a controlled ditching following indications of a failure of the main gearbox (MGB) lubrication system and, subsequently, a warning indicating failure of the emergency lubrication system.
"All passengers and crew evacuated the helicopter into a life raft and were subsequently rescued. Two passengers sustained minor injuries.
"The investigation has identified a 360 degree circumferential crack in the bevel gear vertical shaft in the main gearbox, in the vicinity of a manufacturing weld, causing disengagement of the drive to both mechanical oil pumps."
The helicopter, which had 14 people on board, had been heading from Aberdeen to the Maersk Resilient and Ensco 102 drilling rigs - in the Jasmine field, operated by ConocoPhillips - when a warning light came on.
Operators Bond temporarily suspended flights of the same type of aircraft last week while a "detailed root cause investigation" is carried out.
The firm released a statement on Sunday morning, which said the AAIB report was "consistent with Bond's own engineering analysis."
The statement continued: "In the light of the AAIB interim Service Bulletin Bond Offshore Helicopters Ltd. will continue the flight suspension of the EC225 and now in addition the AS332L2 helicopter.
"Bond Offshore Helicopters Ltd. is working with Eurocopter as a matter of priority in finding a solution that will enable the helicopters to be returned to service."
"The maintenance procedures adopted by Bond Offshore Helicopters Ltd. are of the highest standards with safety being the company's principal concern at all times. It was that focus on safety that was the reason behind the decision to suspend flights of the EC225 having considered the AAIB Service Bulletin."
Bill Munro, managing director of Bond Offshore Helicopters, added: "The skill and training of Bond's pilots has been witnessed at first hand. Our passengers can be confident in Bond as the principal crew change operator in the North Sea".
Members of the Helicopter Safety Steering Group are due to meet on Monday to discuss the incident.