St John is looking into why an ambulance burst into flames this morning

The vehicle was travelling to Auckland City Hospital, but pulled over at Otahuhu Station after the driver noticed smoke.

A spokeswoman says everybody on board was safely evacuated, including a patient, their caregiver and a medical assistant.

Witnesses say the ambulance was well ablaze and there were large plumes of grey smoke, and explosions.

Fire and Emergency says the cause of the blaze is not yet clear.