A woman is dead after a medical event as she travelled in a vehicle along one of Hamilton's main arterial routes this afternoon.

St John Ambulance central region spokesman Mark Tregoweth said they were called to Avalon Dr/State Highway 1 at 2.28pm today.

On arrival they found a female patient but pronounced her dead at the scene.

Mr Tregoweth said she appeared to have died following a "medical event".

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Detective Sergeant Will Loughrin of the Hamilton CIB said the incident was not suspicious.

"On the arrival of Police officers discovered a female deceased in a vehicle. The matter is not considered suspicious and has been reported to the Coroner. Police have been in contact with the deceased's family and on behalf of the NZ Police I would like to express our condolences to them."

It's unclear how many people were in the vehicle at the time.