A trapped driver has been freed after a truck and trailer carrying onions rolled into a ditch on Attewell Rd in Pukekohe.
Emergency services were called to the scene, between Burrow Rd and Upper Queen St, about 7.20pm.
The driver of the truck was trapped and initially thought to be critically injured, Northern fire service spokesman Scott Osmond said.
However, Osmond later said when emergency crews freed the driver he was found to be in a "moderate condition".
A police spokesman said the "truck is on its roof and it's leaking diesel".
Emergency crews have since left the scene.