St John said one ambulance and one manager had rushed to the scene.
"St John treated and transported one patient in a critical condition to Auckland City Hospital," a St John spokeswoman said.
EMERGENCY SERVICES INCIDENT
UPDATE 1 - 3:50PM Due to an emergency services incident at Kingsland Station, please expect delays and cancellations along the Western Line. Services will terminate at Morningside. Please use scheduled bus services in the meantime. Updates to follow. pic.twitter.com/Z1NJUlOnG9
The serious incident will add to delays for commuters on Auckland's road and public transport network after two trucks crashed on the Auckland Harbour Bridge earlier, shutting down lanes the motorway.
"Due to an emergency services incident at Kingsland Station, please expect delays and cancellations along the Western Line," Auckland Transport tweeted.
"Services will terminate at Morningside. Please use scheduled bus services in the meantime. Updates to follow."