Southern Line services were to continue as normal between Britomart and Papakura, using the one open track from Parnell.
Onehunga Line services were to run to Penrose, an AT spokesperson said.
A fleet of rail replacement buses was expected to take passengers to their final downtown destination.
Only one platform was left open at Parnell Station.
“Platform 2 will be used for all services,” the AT spokesperson said.
KiwiRail reported the slip on the line used by the Western and Southern train line services. KiwiRail has been approached for comment.
AT said it would update commuters further.
A spokesperson told the Herald: “Maintainers [are] assessing the extent of the slip and we can update as we know more.”
It follows a slip near Parnell yesterday which caused widespread disruptions across the city.
Passengers using the Western Line had to wait up to 30 minutes at Newmarket to get into the city yesterday morning.