Hazardous materials were being carried by a health service van stolen from outside a doctors' surgery in Kent.
It was also transporting letters between consultants and doctors from several local surgeries when it was taken from outside the Central Surgery in Cheriton Road, Folkestone.
It is understood the driver left the keys in the ignition when he went in to the surgery. The van also contained a tray of 25 sample pots and needles which, although sterile and securely packaged, could be harmful.
A spokesman for the NHS Trust said the materials on board may be dangerous for children, or people with medical conditions.
Vans run between William Harvey Hospital in Ashford and local GP surgeries twice a day, transporting patient samples and letters between consultants and doctors.
Despite the potentially sensitive nature of what is in the vehicle, staff at the East Kent Hospitals NHS Trust are telling patients that they should not worry.
Clinical director of pathology for the trust Dr Ruth Lapworth, said: "The information is not really useful to anyone else but it could be sensitive."