Two people were seriously injured in a crash on the A47 near Lynn on Thursday evening.
An investigation has been launched into the incident, which happened near the Pullover roundabout shortly before 6pm.
A Norfolk Police spokesman said a silver Vauxhall Zafira and a silver Peugeot 206 were in collision around 300 metres from the junction, heading towards Wisbech.
Two female passengers in the Peugeot, which came to rest in a ditch, were taken to the Queen Elizabeth Hospital with serious head, back and leg injuries.
However, their conditions were not thought to be life-threatening. No-one in the Vauxhall was injured.
Police want to hear from anyone who witnessed the collision, or who saw either of the vehicles involved prior to it.
Anyone with information is asked to contact the Norfolk Police serious collision investigation team, based at Swaffham, on the non-emergency 101 number.