Bad practice by hospital anaesthetists was blamed yesterday for the death of a nine-year-old boy during a minor operation and accidents involving 12 other patients.
Tony Clowes, from Dagenham, Essex, was starved of oxygen during a finger operation at Broomfield hospital, Chelmsford, last July because a breathing tube was blocked.
Police launched an inquiry into possible medical sabotage. But a year-long inquiry, which also looked at 12 similar incidents of blocked anaesthetic tubes over a 14-year period, found no evidence of criminal behaviour.
Doug McIvor, of the Medical Devices Agency, who was involved in the joint police and Department of Health investigations, said: "It is a storage problem and it relates to bad practice."
Thirty police forces investigated the 13 accidents involving blocked anaesthetic tubing, which occurred at 11 British hospitals between 1988 and 2001. The other mishaps, which were not fatal, came to light after publicity about Tony's death.
Forensic experts said the problem centred on small L-shaped bits of tubing, called angle pieces, which are used to connect anaesthetic pipes. They should be discarded after a single use but were sometimes washed and reused. When stored in the same place as intravenous drips, small plastic caps from the drips were able to become lodged inside the angle pieces, leaving them blocked.
The angle pieces are no longer reused and are now individually wrapped for safety.