Wellington's commuter train services are back operating on their normal schedule after causing disruption for thousands of people.
Earlier, thousands of people who catch the Hutt Valley and Melling line morning trains were being asked to work from home if possible, or wait for bus replacements.
It came after an old rail from the Kāpiti line, which was left on the side of the track during replacement work, caused damage to a component near the wheels of trains that drove through.
Metlink said about a quarterof the Matangi fleet needed inspecting or repairs.
KiwiRail - which maintained the lines - said it was working with Metlink to understand how and when the damage to the trains occurred, and whether the rail next to the tracks might have moved somehow.
Metlink replaced trains with buses last night, and will do the same during morning peak travel today on the Hutt Valley and Melling line services. The Kāpiti line will run on a reduced timetable.
While Johnsonville and Wairarapa line are not affected and will run as normal.
RNZ reporter Michael Cropp at Wellington Station told Morning Report foot traffic was fairly free flowing and some commuters had opted to drive in instead of putting up with buses.
Hutt Valley commuters are describing a slower than usual trip to work today, as they're forced to take the bus or drive into Wellington.
One Upper Hutt resident who took a bus replacement service said it took her an extra half hour to get into the city.
She said these disruptions were too common, and had a flow-on effect to her business because they resulted in staff arriving late or needing to leave work earlier than usual. This meant customers did not get served on time.
Another person who drove in from Upper Hutt by herself said she felt guilty taking the car and was conscious of carbon emissions.
But it's not clear how long repairs would take or whether they'll be done by afternoon peak travel time.
In a statement last night, KiwiRail apologised for the disruption and said an investigation was underway.
"A full inspection of the Wellington network is being undertaken to ensure that there are no other objects that could contact these components."
Operator Transdev would not say how many trains were damaged, but said repairs started yesterday afternoon.