The norwalk virus has been deemed the most likely cause of the mass sickness on a British Airways flight from London in October which struck at least 30 crew and passengers ? many of them children.

However an investigation by the Bermuda Health Department has failed to confirm it because of a lack of specimens.

The sickness spoiled the holiday for many Bermudian children who were returning for half-term from British boarding schools.

The norwalk virus causes severe sickness for up to two days but is not serious. People can pick up the disease by eating contaminated food or liquids or through contact with carriers.

Yesterday Chief Medical Officer John Cann said: ?It?s clear there was a Norwalk-like virus.

?We detected it from a sample from one passenger but you have to have a clear link. We didn?t have enough specimens. Most likely it was in the water.?

Children are particularly susceptible to the virus. Dr. Cann said the virus can be killed off by running extra hot water through the plumbing system and BA had done this as a precaution at the time.

He said: ?British Airways sterilised and cleaned the plane. They did that even before they knew what was going on. They didn?t want to taken any chances.?

The norwalk virus has also shown up on cruise ships in recent years.