An evaluation car has derailed in a tunnel near Port Chalmers this morning, and has the potential to cause diruptions to freight services.
A KiwiRail spokesman said the incident happened about 8am.
The four-person crew was uninjured, and in accordance with procedure they have walked out of the tunnel.
Staff are on site to recover the vehicle, which is used as part of track maintenance programmes.
Freight services may be disrupted, depending on how long the recovery takes, he said.
In line with normal procedure, the police and fire service were notified and are in attendance.
"An investigation will be carried out. Any comment on cause would be premature at this stage," he said.
