(Updated Friday 10 October, 10.55aM)

State Highway 1 between Windermere and Swamp Roads has been cleared and reopened following a six-vehicle crash on Thursday afternoon.

Police said the vehicles involved included a van, two utes and three cars.

Four firetrucks - two from Ashburton, one from Hinds and one from Geraldine - responded to the crash, Fire and Emergency New Zealand said.

One person was trapped in a vehicle on the crews' arrival and had to be retrieved.

Hato Hone St John said three helicopters, two ambulances, one first-response unit and rapid response unit were sent to the scene.

They said one person in critical condition, one in serious condition and one in moderate condition were helicoptered to Christchurch Hospital.

Two others in moderate condition were transported to Christchurch by ambulance.

One other person was in minor condition but did not require transport to hospital.