State Highway 6 is now open under stop/go traffic management at the site of a crash which left one person critically injured.

Drivers should expect ongoing delays on SH6 in the Pelorus area until the incident is resolved, and the highway is fully reopened.

NZTA Waka Katohi is warning drivers to also take extra care when travelling through the area, observe all traffic management measures in place and follow instructions from emergency services and road crews.

One person was in a critical condition following the crash near Pelorus Bridge this morning.

State Highway 6 in Marlborough was completely closed for three and a half hours after the single vehicle crash was reported at 10:30am.

The Police Serious Crash Unit have been at the scene carrying out investigations.

A Hato Hone St John spokesperson says they responded to the crash with one helicopter, two ambulances and one First Response Unit.

"Two patients were assessed by the ambulance crews at the scene, with one in a moderate condition transported to Wairau Hospital by ambulance in Blenheim.

"The other person was flown to Wellington Hospital by helicopter in a critical condition.”

Updates on the highway’s status can be checked online. Drivers are encouraged to check road conditions before they travel.