Emergency services have been called to a serious crash in Sheffield.

A police spokesman said they were called to State Highway 73 at the intersection with Deans Road.

The two vehicle crash was reported at 2:50pm.

Initial indications are there are serious injuries, the spokesman said.

A St John spokesperson said one ambulance, two operations managers and one first response unit attended.

Two patients, both in moderate condition, are being transported to Christchurch Hospital.

It referred all other inquiries to police.

Motorists are advised to avoid the area and expect delays.

NZTA said State Highway 73 was closed between Bulls Road and Auchenflower Road intersection.

Road users are advised to delay their journey or avoid the area if possible.