there are two possible ways watermelons could have caused infection. One is that the surface of the melons could have been contaminated with Salmonella bacteria which may have transferred on to the flesh of the melon during the cutting process. The second is if the melons were stored or washed in contaminated water, the salmonella bacteria could have got into the flesh of the melon through the cut stem. "Although it's too soon to say with certainty what the likely cause of infection is, early indications suggest that a number of people became unwell after eating watermelon," said Dr Bob Adak, head of the gastrointestinal diseases department at the HPA, which has been monitoring the outbreak in England, Wales and Northern Ireland. Read Full: UK: Salmonella identified in watermelons