The Transport Accident Investigation Commission has found an electrical fault caused a Wellington train to short circuit and catch fire.

It was travelling between Paremata and Mana stations in April 2008, when the driver experienced problems with the traction motors.

Each attempt to depart from the Mana platform resulted in an immediate traction motor overload and the train's electrical equipment cabinet caught fire. Passengers were evacuated and the blaze was extinguished before the fire crews arrived.

The commission says the fault in the traction motor had been developing throughout the previous week, yet weakness in the fault-reporting system mean it went unnoticed.