Three people injured in Redwood Pass crash outside Blenheim

The aftermath of a crash near Blenheim today. Photo / Nelson Marlborough Rescue Helicopter

A 70-year-old woman is in a critical condition after a head-on crash near Blenheim.

Two cars collided near Smiths Overbridge in Redwood Pass at 3.06pm.

A police spokeswoman said originally it was thought two people were trapped, but one person had made it out of the vehicle.

Two cars were involved in the crash. Photo / Nelson Marlborough Rescue Helicopter

Nelson Marlborough Rescue Helicopter transported a 70-year-old Blenheim woman to Wellington Hospital in a critical condition.

Earlier, police said two people are in a serious condition, while one other had moderate injuries.

"The car was down a bank so it wasn't blocking the road," she said.

Police were diverting traffic off Redwood Pass Rd.

Train control was also advised.