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.
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.