SYDNEY (AP) - Australian investigators say a poorly built pipe leaked oil and caused the dramatic disintegration of a Qantas superjumbo jet engine during a flight in 2010.

The Rolls-Royce engine explosion aboard a Qantas A380 forced an emergency landing and was the most significant safety issue an A380 had ever faced since it began passenger flights in 2007. No one was hurt, but A380s around the world were temporarily grounded.

The Australian Transport Safety Bureau released its final report on the emergency on Thursday. The agency concluded the wall of an oil pipe inside the engine was too thin. That caused an oil leak, which sparked a fire that led to the engine explosion.

Rolls-Royce says it has improved its manufacturing and design processes.