The Transport Accident Investigation Commission (TAIC) blames three rail incidents in 2008 on inadequate maintenance practices at the rail depot at Westfield in Auckland.
The incidents included two fires and a brake housing coming loose and falling on the rail line, derailing a train.
TAIC's report says at the time there was a blurring of responsibilities for maintenance of the trains.
It also noted a breakdown of relationships at senior management level between the then Auckland Regional Transport Authority, train operator Veolia and KiwiRail.
The report says the fires were due to an oily residue collecting on top of the motors, and the brake housing fell because the securing key had either failed or worked loose.
There were no injuries.
TAIC says in light of subsequent improvements in safety practices it has no recommendations to make.
