Two people have been hurt after a truck rolled about 8am near Kawerau.
Senior Sergeant Malcolm Collins said police and ambulance services attended the scene.
Mr Collins said there were two people in the vehicle and, from what information they had so far, it was due to black ice.
There were no other vehicles involved, he said.
Mr Collins said road crews also came out and worked on the road making it less slippery.
He advised drivers look out for any pieces of road which were sheltered, such as from trees or hill sides, and were not getting the sun.
Mr Collins also advised people to drive to the conditions, slow down at corners and to drive as if they were expecting the black ice.