A pillion passenger has been seriously injured following a crash between a car and motorcycle, near Dome Forest.
Emergency services are attending a serious crash on SH 1 near Kaipara Flats Road.
"One lane of the road is open but traffic has built up in the area and is moving very slowly," says police.
"Motorists are being asked to please use the alternative route, SH 16 instead."
The Serious Crash Unit has been advised.