Blood samples being taken from Medway Maritime Hospital by a motorbike courier service have been mislaid en route to London.
A spokesman for the hospital said the consignment of 14 samples went missing between the hospital and the Bean interchange on the A2, near Bluewater, in Dartford.
The route which the bike took was from Gillingham town centre to the Medway Tunnel and then on to the A2.
The samples were packed in ice in a white polystyrene 12-inch cube container, addressed to the Haemophilia and Haemostasis Department at the Royal Free Hospital in Hampstead, north London.
The Medway Maritime Hospital spokesman said: "The risk to the public is absolutely minimal.
"If a member of the public finds this container, or parts of it, they should leave it and contact the police.
"Medway NHS Trust is conducting an urgent investigation into this matter in conjunction with the courier."