People travelling through New Lynn in either direction will need to transfer between trains at the New Lynn stop. There will be staff on site to help passengers.
The subsidence issue was discovered during a routine inspection on Monday.
KiwiRail staff carrying out the inspection spotted movement in an overhead electric pole.
Speed at that particular location was then reduced to 25km/h as preliminary investigations took place. Investigations continued yesterday which ultimately confirmed there was subsidence underneath the track.
Underground investigations will determine how soon work can be completed to allow train services to resume normal service, AT said.
Meanwhile, some delays are also expected after an earlier truck breakdown just after the Mt Wellington Highway off-ramp.
Waka Kotahi NZ Transport Agency reported the breakdown about 6.45am. It was blocking the left northbound lane and motorists were advised to pass with care.
It has since been cleared of all lanes. But drivers are told to allow for extra time, still, as northbound delays ease.
