UPDATED: A person is in a critical condition after being trapped by a tractor on a farm in Aongatete.

St John has airlifted one patient in a critical condition to Waikato Hospital, a spokesperson has confirmed.

Ambulance received a call at 2.47pm to the incident on Hume Road and one ambulance and one helicopter from Hamilton have responded, says the spokesperson.

EARLER: Emergency services are working to free a person trapped by a tractor on farm land in Aongatete this afternoon.

Fire and Emergency, St John Ambulance and a rescue helicopter are present at the scene on Hume Road.

Fire and Emergency New Zealand northern communications shift manager Craig Dally says they are currently working to free a person who is trapped by the leg.

A police spokesperson says they were notified of the incident at 3pm and are enroute to the scene.

St John were unable to provide information about injuries at this time.

A spokesperson says they are assessing one patient at the scene.

A Wright Road resident says he saw a helicopter land nearby and has heard lots of sirens go past.