Six E. coli cases at Tri Ceffyl Bach nursery, Anglesey
Three new cases of E. coli have been confirmed in an outbreak at a children's nursery on Anglesey, taking the total number to six.
Tri Ceffyl Bach Nursery in Amlwch was closed as a precaution last Thursday.
So far 58 people have been tested with tests being offered to anyone associated with the nursery.
Investigations into the source of the outbreak are ongoing, but health officials said it was difficult to determine when children are involved.
Dr Chris Whiteside, of Public Health Wales, said: "Given the nature of this infection it is not unusual for more cases to be identified amongst children attending the nursery.
"This is why the nursery was asked to close and the children and staff were asked to be tested.
"Investigations into the source will continue. However, it can be difficult to identify a definitive source in an outbreak like this because the bug is so easily spread where young children are concerned."
He added: "In Wales about 80 cases of E. coli O157 are diagnosed each year.
"Considerable effort is going into providing advice and collecting information locally that will help control this outbreak.
"People can become infected with E. coli O157 by eating contaminated food, or through contact with infected people, farm animals or contaminated water.
"It is important to re-enforce the message that this infection can be passed from person to person and so anyone who is ill should observe strict personal hygiene to avoid spreading the infection."
Public health officers and environmental health teams from Betsi Cadwaladr university health board and Anglesey council are investigating.
Symptoms of E. coli O157 range from mild diarrhoea, stomach cramps and fever to severe bloody diarrhoea.
The incubation period can range from one to 14 days, but is usually three to four days, and people with E. coli O157 are usually ill for up to two weeks.