Three slips, costing an estimated $500,000 to repair, had occurred along the main trunk line between Dunedin and Waitati because of waterlogged soils, a KiwiRail spokeswoman said.
The most recent was above Deborah Bay, just south of the Mihiwaka Tunnel, which caused the rail line to be closed on Friday night after monitoring of the site showed issues that ''gave us cause for concern'', the spokeswoman said.
Staff assessed the situation on Saturday morning and trains were let through again but only during daylight hours, she said.
''At this stage, we are still moving trains through the area.''
The trains were being piloted, which meant they travelled at reduced speed and with a track inspector on hand. It had meant schedules had to be adjusted for some domestic freight traffic, she said.
''We are working with our customers to prioritise freight movements between Christchurch and Dunedin and ensure that they are kept informed.''
In the meantime, a temporary solution of realigning the track was being examined, which could take two weeks to construct.
''This will require rock and general fill to build up a new formation for the track.''
A longer-term solution to repair the embankment was also being investigated and, depending on the weather, could take six months to complete.
The wet weather had caused other slips, including a smaller but similar one in Henry St, above Port Chalmers, and there had been a few track-side slips in Church St.
''Half a dozen small surface slips between Dunedin and Waitati have been cleared in the last fortnight.''
