Watermelons may be the source of a salmonella outbreak across the UK which has affected 35 people, leading to one death.
The Health Protection Agency (HPA) said 35 people in England, Wales, Scotland and Northern Ireland have been infected since the beginning of December - three times higher than is normally expected in a two-month period.
A total of 26 cases have been confirmed in England, three in Wales, one in Northern Ireland and five in Scotland.
One of these people, who has not been named, has died although they had serious underlying health complications. All the cases involved a strain of Salmonella Newport infection.
In the Republic of Ireland there have been another four cases and 15 reported in Germany.
The 30 cases in England, Wales and Northern Ireland were among people aged six months to 85.
Some 70% of cases have involved women and the East of England is the region most affected.
The HPA said very early indications suggest the outbreak may be due to eating watermelon.
In November, as part of a local food survey, the HPA identified Salmonella Newport from a ready-to-eat sliced watermelon.
Some people who then became unwell were found to be infected with the same strain.
The HPA has also spoken to 15 affected people and found 10 had eaten watermelon in the three days before they became ill.
Symptoms of infection include diarrhoea, vomiting, abdominal pain and fever but people usually get better in four to seven days.
Some may need antibiotics and complications include blood poisoning or a localised infection.
Experts believe there are two ways watermelons could have become contaminated with salmonella.
Bacteria on the surface of the melon could be transferred to the flesh of the melon while it is being cut up, or may be transferred if melons are stored or washed in contaminated water.
Dr Bob Adak, head of the gastrointestinal diseases department at the HPA, said: "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.
"This has also been noted in the cases in Scotland and Germany although further investigation is ongoing.
"It's important to remember the risk of becoming unwell after eating watermelon is very low.
"These cases only represent a very small proportion of total consumption.
"It is always advisable to wash fruits and vegetables - including watermelon - before consumption to reduce the risk of possible illness.
"Colleagues from the Food Standards Agency are part of the outbreak control team and they are working with us to identify the source of this outbreak."
Many different foods have previously been identified in Salmonella Newport outbreaks in the UK.
The largest one, in 2004, was linked to people eating lettuce at restaurants and takeaways.
Around 200 cases of Salmonella Newport are reported in England, Wales and Northern Ireland every year.
There are more than 2,500 different types of salmonella species. Salmonella Newport causes a similar illness to other forms of salmonella infection.