A rescue mission is underway on the South Island’s West Coast after a car was seen going into a fast moving river and being swept away.

A police spokeswoman said police are responding to a report of a vehicle in water on Wanganui Flat Road at Harihari.

A person and a dog are reportedly in the vehicle.

The call came in about 9.15am.

Fire appliances from Harihari have been called to the scene.