River Rd in Tuakau is still closed after chemicals were spilt from a serious crash earlier today.
As a significant clean-up is under way part of the road will be closed for around three more hours.
Traffic diversions remained in place from River Rd to Whangarata Rd, and River Rd to Tuakau Rd.
A hazardous chemicals unit from South Auckland attended the accident scene after concerns one of the vehicles was carrying agricultural chemicals.
Fire Service northern shift manager Jaron Phillips said two people were injured in the crash which happened at midday.
The second patient had minor injuries.
The most critically injured person was still being cut out of the vehicle ahead of being flown by rescue helicopter for treatment.