Two people have been injured in a jet boat crash.

Emergency services were called to a boat crash on the Waimakariri River at Clarkville at about 5.10pm.

A police spokesman said four people were on the boat at the time of the incident.

A helicopter was sent to the scene.

Two people were taken to hospital, one in a serious condition and the other with moderate injuries.

Authorities are investigating the cause of the crash.