Motorists travelling between Picton and Blenheim should expect delays following a three-vehicle crash that has left a person critically injured.

Emergency services were called to the crash at Tuamarina, between Bush and Para roads, about 6.30am.

A vehicle hit a wire barrier and one of the occupants was ejected; the person suffered critical injuries and will be airlifted to hospital.

Two other people are being treated for minor and moderate injuries.

The road is expected to be closed for some time and the Serious Crash Unit has been notified.

Diversions are in place and motorists are asked to expect delays and take care.

© Scoop Media