Photo: Auckland Transport
Train services in Auckland have mostly been restored, after grinding to a halt earlier on Thursday.
Now, all rail services are operational, with the exception of the Onehunga line which has been suspended until further notice.
Auckland Transport said commuters should expect delays and some cancellations while the network recovered from the stoppage.
'Error' by a software engineer
KiwiRail chief capital planning and asset development officer David Gordon told Checkpoint a software issue is what caused the trains to be delayed.
He put it down to a miscommunication between the team that monitors the train control software and the network team.
"It is just a genuine error by a software engineer, who should have left it [the software] alone."
"The initial fault is quite clearly KiwiRail's" - David Gordon
The signalling system was down for 13 minutes, but there was a cascading effect, he said.
"We lost the detection of the signalling system, so when that happens the system is configured to what is called fail-safe. Now that doesn't mean it doesn't fail, but what it means is that when you have a failure of that nature, the lights go red.
"I can't comment as to why it is still happening now, that's with the train operating themselves but I do respect the fact that if you have a disruption in the timetable, it takes time to settle down.
"The initial fault is quite clearly KiwiRail's. We absolutely own accountability for the initial fault.
"The cascade is actually something that is shared between ourselves and the above rail operator and I'm not in a position to say whether they have been efficient or not.
"Auckland One Rail are a very good global operator, I'm sure they've done their very best to avoid it."
In an earlier travel alert Auckland Transport said the stoppage was due to a KiwiRail track infrastructure issue meaning all rail services had been held until further notice.
Travellers were advised that buses were accepting all AT Hop cards and rail tickets.
Auckland councillor Richard Hills criticised KiwiRail for shutting down the entire network.
"I'm not an engineer but surely there's a better way to manage a track issue than closing down an entire network."
It seemed that although the government had invested $330 million to upgrade the track network it seemed to be less resilient than before.
"I'll say it again KiwiRail must up their game urgently."
There have been a series of train cancellations and delays this month, which have angered Auckland mayor Wayne Brown.
Thousands of commuters trying to travel on the Western, Southern and Eastern line train services were affected over one three-day period.
KiwiRail said it was working hard to upgrade train tracks so they wouldn't be affected by heat restrictions.
Some trains have been cancelled as speed restrictions were imposed when the tracks became too hot.
The transport agencies overseeing the rail network said the problems causing delays and cancellations needed to be promptly resolved.
Senior leaders from the agencies attended a please explain meeting with Brown on 14 February.
In a joint statement, Auckland Transport, KiwiRail and Auckland One Rail said they would keep Brown updated as they worked together to fix problems.