A person has been critically injured after being hit by a train at a south Auckland railway station.

It is believed the person fell off the platform before they were hit.

Police were called to the Otahuhu Station just after 3pm.

The person was rescued from under the train at 3.30pm.

They have been rushed to Middlemore Hospital in a critical condition.

Two Fire Service crews are also at the scene.

Auckland Transport said the call out could cause major delays to commuter rail services this afternoon.

The agency said people should prepare for delays and reduced rail services.