Train services are back on track in the Wellington region, but lines in the South Island remain down after Spark outages overnight, KiwiRail says.
Thousands of commuters for all the capital's services faced delays today when a fibre outage lasted more than two hours longer than planned.
The outage at 3.30am was due to last about an hour, but services were not restored until just before 7am.
"The outage has been restored so the commuter service is going okay in Wellington now maybe some trains have some slight delays as they catch up through the morning," KiwiRail senior communications advisor Ron Murray said.
There was also some outage activity in the South Island relating to Spark's server in Christchurch, he said.
The Midland Line at Arthurs Pass and Otira, going through to the West Coast had been affected.
"We're waiting to hear when those outages are restored to enable (freight and passenger) trains to go through," Mr Murray said.
KiwiRail was investigating the incidents.
The latest outage comes a week after a fire beside a Wellington line resulted in dozens of passengers being trapped on a train.
A scrub fire had caused a tree to fall on power lines near Takapu Station, in the Wellington suburb of Tawa, on February 25.
About 80 people were trapped on the train while fire crews extinguished the blaze.