Three people have been transported to Whangarei Hospital following the crash.
One female is status 1, critically injured, and two children who were in the car are status 2, seriously injured, and status 3, moderately injured.
The truck driver has leg injuries that are not serious.
The police Serious Crash Unit is at the scene along with the Commercial Vehicle Investigation Unit.
The road is expected to be closed for a few hours while police survey the scene. Traffic will continue to be diverted through Kamo.
UPDATE 9.21am
The bypass will be closed for a while and all traffic is being diverted through Kamo.
A reporter at the scene said traffic is backed up on Snake Hill.
Police, three ambulances and two fire engines are at the crash.
8.57am
The Kamo bypass is closed after a crash this morning.
Police said a truck and a car collided just south of Great North Rd, Whangarei about 8.50am. One person is trapped but injuries are unknown at this stage, police said.
An ambulance is on its way.
The bypass will be closed from Great North Rd south.