A truck that plunged into a central North Island stream this morning was not carrying any radioactive substances, according to the Fire Service, but its driver is still missing.
Radiation fears were sparked after the fully-laden B-train truck, marked with a radioactive materials sign, was found in the Waihohonu Stream on State Highway 1 between Waiouru and Turangi.
Emergency services were called to the scene outside the Tongariro National Park boundary at 4.22am.
Fears over the truck's spilled cargo have forced the closure of the Desert Road and the nearby Rangipo Power Station, while the driver of the truck was yet to be located.
Fire Service northern communications shift manager Jaron Phillips this morning confirmed no radioactive substances were found on the truck.
"We've gone through the manifest and the company as well, and it's confirmed that is was carrying no radioactive substance," he told APNZ.
Mr Phillips said concerns were raised because the entire contents of the truck were in the river.
He said the truck contained aerosol containers and was also believed to contain an environmentally hazardous insecticide called alpha-cypermethrin.
Numerous organisations are responding to the incident, including the local council, police, the Fire Service hazardous materials unit and the National Radiation Laboratory.
Communications in the remote area were difficult but a satellite communications channel was now up and running.
Police said SH1 would remain closed for a considerable time and diversions were being put in place.
They said the safety of people at the scene and the wider public was paramount.
Turangi volunteer fire crews were replaced earlier this morning by three crews from Rotorua's Hazardous Chemical Unit, who remain at the scene.
Chief Fire Officer Tong Kingi said the operation would be a long one, due to the amount of debris.
"There is stuff everywhere. It was a full laden B-train truck with a soft curtain side. The majority of spilt material is around the truck."
Mr Kingi said while the Waihohonu Stream is referred to as a stream, it was more like a river and was reasonably fast-flowing.
"When we arrived early this morning it was not clear how much debris had fallen into the stream because it was still so dark, but on daylight, we could see quite a bit of material trapped in whirlpools and around rocks in the stream.
"It's a massive environmental operation," he said.
Genesis Energy spokesman Richard Gordon said the Rangipo Power Station had been closed as a result of the crash.
The 120 megawatt power station, which generates enough electricity to power about 100,000 homes, turned off its turbines about 7.30am.
"We're not sure at this stage what material is in the river from the truck crash, and we're taking a precautionary approach. We've got intake screens to stop large things going through into the Rangipo turbines, but we're not sure what material was on the truck."
Mr Gordon said it was unclear when the power station could reopen.