Auckland Transport is still investigating the fault that disabled one of its new electric trains, disrupting peak hour services this morning.
The electric train lost power and was stranded near Penrose soon after 6am, causing southern services to be diverted through the eastern line.
Delays of up to half an hour built up on the network, and buses were brought in to help move passengers from Pukekohe and Waitakere stations.
The agency said it was not yet clear whether the fault was with the train itself, or in the overhead power supply.
Auckland's rail services are expected to go fully electric late next month.