Two people have been rushed to Whangarei Hospital after their cars collided in a passing lane north of Kaiwaka just after 7pm.
A pregnant woman has been airlifted while a man has begun the 45 minute journey to the hospital by ambulance.
Both needed to be removed from their vehicles by emergency services and are in a serious condition.
It took several hours for the debris to be cleared away and police warned motorists to expect delays. All lanes have since been reopened.
The Serious Crash Unit is at the scene and investigating.