When preparing documentation on 19 October 1999 for the consignment of sources from Sellafield site to Drigg Low Level Waste Disposal Site, it was discovered that a Type A transport container was proposed when a type B container was required to comply with the Transport Regulations for the quantity of material to be transported. The consignment was therefore suspended. A review of previous transfers revealed that the incorrect package has been used for similar transfers between the Sellafield and Drigg sites for a number of years. Consignment in an incorrect package is being regarded as equivalent to breach of a limit or condition. A mangement investigation is now underway to determine the cause of this incident. There has been no safety impact and there are no environmental or health implications.