A train derailed at National Park yesterday afternoon.
Police said six carriages came off the tracks about 4.30pm and were blocking Carroll St.
No gas or dangerous goods were on board, and no one was injured.
Former radio host Iain Stables witnessed the train coming off the tracks.
"There was so much dirt and dust coming from behind it, and then it was almost like in slow motion, like seeing a building being demolished.
"The first wagon came off the track and then the other ones flipped over it like dominos.
"The driver got out and was walking around and he seemed okay. It doesn't look like anyone has been injured."
Mr Stables said the main track was completely blocked.
"If you've ever stood there and seen a train roll over, it is unreal."
Kiwirail spokeswoman Julie Buchanan said: "As a result of the incident, part of the train is blocking the Fisher Rd level crossing, and freight services on that section of the North Island Main Trunk line are going to be disrupted."
KiwiRail was working to clear the site.
"While it is too early to say what caused the derailment, we will be investigating." NZME