Two tourists and an elderly woman have been taken to hospital after a head-on smash between two rental cars near Burnham about 1.30pm.
Both lanes of State Highway 1 were closed and diversions have been in place.
Police said it appeared a woman in her 70s, driving north in a rental car, drifted cross the centre line, colliding with another rental car carrying a French couple travelling south.
The drivers of both cars were taken to hospital by helicopter while the passenger in the southbound car was taken to hospital by ambulance.
The driver in her 70s was described as in a serious but stable condition in hospital. The French couple were in a stable condition, said police.
Police said they hoped to clear the crash site on SH1, just south of Aylesbury Road, before 5pm.
Less than an hour earlier, a crash blocked one lane of the Old Waimakariri Bridge. A car had rolled about 12.45pm, but no one was taken to hospital.
The southbound lane of the bridge was briefly blocked, but has since been cleared.
- The Press