A woman has been transferred to Christchurch Hospital after a car struck a power pole on State Highway 3 in Kaitoke, near Whanganui.

The crash occurred about 12.30pm on Thursday and caused the highway to be closed, with two people taken to Whanganui Hospital in serious condition.

Te Whatu Ora Whanganui said one patient, a woman, was treated and then transferred to Christchurch Hospital while the second patient, a man, was treated and discharged.

A Powerco representative said the incident involved a car hitting a power pole on the highway, resulting in power being cut to 224 customers and bringing powerlines down.

A field crew was dispatched to make the site safe and assess the damage.

Just over 100 customers were reconnected by 1pm, with power restored to the remaining 107 customers by 9.30pm.

Repairs are ongoing.

A Fire Emergency New Zealand spokesperson said the lines caused a small fire on the grass next to the road but not on the car.

Two Whanganui Fire Station crews and a support truck were deployed to the scene.

Due to the fire and the live wires, the two people in the car stayed put until crews had the fire extinguished and Powerco had isolated the power supply away from the downed wires.

Once the people were extricated from the car and taken to hospital, the fire crews stayed on-site to assist with traffic and scene safety while the lines were repaired.

Crews left the scene about two hours after they arrived.

Police said the vehicle was removed from the scene and roads were reopened by around 3pm.

Inquiries to determine the circumstances of the crash are ongoing.