UPDATED 4.01pm: A vital South Island highway has reopened, after a serious crash saw two people airlifted to hospital.

The crash happened about 15 kilometres west of Hanmer Springs, and closed the turnoff onto the Lewis Pass.

Two people with moderate to serious injuries were airlifted to hospital after their car crashed into a pole earlier this morning.

While the Lewis Pass has reopened, the New Zealand Transport Agency says there may be some slight delays near the crash scene.