A fault at Britomart train station which left commuters in Auckland stranded on Thursday morning has been fixed for the time being.
Signals and several points mechanisms, which allow trains to move from one track to another, shut down at the beginning of peak hour.
Southern and western lines were terminated at Newmarket with passengers having to take a bus the rest of the way into the city.
Ontrack says contractors suspect the problem was electronic or software related, but are not entirely sure yet.
The agency says the backlog from the delays is still slowly clearing.