State Highway 1 in North Canterbury has been closed following a serious four vehicle crash involving a horse float.

Police said emergency services were called to SH1 at Domett Road at about 10.45am after reports of a crash involving four vehicles.

There has been no confirmation on the condition of the horse.

The Serious Crash Unit has been advised and the highway was closed while emergency services worked at the scene.

St John said it was notified of the crash and responded with two ambulances, a PRIME responder, two rescue helicopters and two operations managers.

Two patients in serious condition were airlifted to Christchurch Hospital.

One additional patient in a minor condition was transported by road to Christchurch Hospital.

The New Zealand Transport Agency said the crash occurred on SH1 at Domett Road, west of the intersection with Darrochs Road near Domett.

The highway has been closed between Ethelton Road and Darrochs Road while emergency services deal with the crash.

Motorists have been urged to expect delays and consider delaying travel through the area.