KEY POINTS:
A freight train has derailed at Huntly closing State Highway One disrupting traffic at the start of the holiday weekend.
The train came off the main trunk line just after midnight, on the level crossing at Bell Street and State Highway 7.
Toll New Zealand's corporate affairs general manager Sue Foley said the cause of the accident is not yet known but an investigation is underway.
Toll owns the freight train that was taking 10 wagons from Auckland to Tauranga. Two containers have fallen on to the highway after the train de-railed.
Ms Foley said the fire service will be at the scene as a precaution while a container carrying paint and chemicals is moved.
She said none of the chemicals have spilt and cranes will be needed to shift them.
Ms Foley said the overlander passenger service between Wellington and Auckland has been affected and passengers will be bussed from National Park to Auckland and Auckland to National Park.
Ontrack, who maintains the rail line, is also looking into the cause of the accident.
Spokesman Kevin Ramshaw said at least 10 wagons were derailed in the accident.
Waikato police spokesman Andrew McAlley said the road will not be opened until 2pm this afternoon.
"There's nothing sinister. It's a simple train derailment at the worst imaginable spot," Mr McAlley said.
He said a shower of sparks was seen coming from under the train before it tipped over.
Traffic has already backed up for several hundred metres, Mr McAlley said.
Northbound traffic is being diverted over the Tainui Bridge and on to Harris St to Rangiriri and back on to State Highway One.
Police are recommending southbound drivers turn off State Highway One at Rangiriri and cross the Waikato River via Murray Rd.
Traffic is also being diverted off State Highway One on to Fletcher St in Huntly but is already congested.
