COPENHAGEN, Denmark (AP) — Norway's Accident Investigation Board says "a fatigue fracture" in the main rotor gearbox caused an Airbus EC-225 helicopter to crash off western Norway in 2016, killing all 13 people on board.

The helicopter was carrying workers from an offshore rig in the North Sea before it went down on Turoey, a tiny island outside Bergen, Norway's second-largest city. Eleven Norwegians, one Briton and one Italian were killed.

The board presented its final report Thursday, which excluded human error and maintenance actions by the helicopter operator.

Agency spokesman Kaare Halvorsen said the gearbox design caused the crash and urged Airbus to revise it.

The crash bore similarities with a fatal 2009 accident off Scotland with a similar type of helicopter in which 16 people died.