The derailment of two wagons on the main south rail line near Waitati on Friday night delayed two trains before damage to the tracks was repaired on Saturday morning, a KiwiRail spokeswoman said.
The spokeswoman confirmed that one of the two wagons which derailed was one of the controversial Chinese-built freight wagons, which have previously come in for criticism.
The two wagons derailed beside State Highway 1 at Waitati about 10.30pm after a bogey on each left the tracks.
It was ''too early'' to tell what caused the derailment, she said.
''We generally have an investigation whenever there is a derailment, but that can take some timeThe container wagons were cleared from the track by a crane ''first thing'' on Saturday morning.
''Very little'' damage was caused to the track and workers had it repaired by 10.45am, when the track wasreopened.
In the meantime two KiwiRail trains were delayed.
''We had a couple of trains due through and we just held them at Timaru overnight.''
However, the trains would still have made it to Port Chalmers on time after the track was repaired, she added.
The derailment on Friday night was the second in the Dunedin area in a 24-hour period.
A wagon left the rails in the tunnel leading into Port Chalmers from Dunedin on Thursday night. Port Otago commercial manager Peter Brown said the wagon was put back on the rails before morning and normal train operations were resumed.