KiwiRail is investigating whether a crash at a station near Wellington was caused by the train driver applying the brakes too late.
The Matangi-class train hit a concrete barrier at the Melling station in Hutt Valley just before 8am on Monday. Nine passengers, one driver and a guard were on board.
KiwiRail said it is thought a mechanical problem was the cause of the incident, but is not ruling out driver error.
General manager of passenger services Deborah Hume told Radio New Zealand's Checkpoint programme an investigation is underway, but extensive tests on the brakes show that they were working properly.
Ms Hume said the driver has told them he put the brakes on and one factor the investigation would focus on is when they were applied. The state of the track at the time is also being looked at.
KiwiRail said it doesn't believe there is a need to check the entire fleet in Wellington.
Meanwhile, the Transport Accident Investigation Commission said two investigators have completed a scene examination and interviewed those on the train.
Spokesperson Peter Northcote said they have downloaded data from the equivalent of a plane's black box, known as an event logger, and this would be examined.
Mr Northcote said the commission's inquiry could take up to a year, but any urgent safety issues would be communicated immediately.
Wellington lawyer Simon Rees-Thomas said he saw several people walk off the train dazed and shocked on Monday morning. He said the train was coming in much too fast and expected the driver to slow down, but it ploughed into the barrier at the end of the line.
KiwiRail said the train has been taken back to Wellington and the Melling line near State Highway 2 was re-opened on Monday afternoon.