Health officials are investigating the possibility that two children who have contracted E.coli may have become infected at a petting farm in Brecon.
The children, who are recovering at home, had visited the Cantref Adventure Farm in the days before their illness.
The farm has stopped direct contact between animals and members of the public as a precautionary measure and is also undertaking a deep clean of the premises.
Two other people, who are family members of one of the infected children, have also tested positive for E.coli O157 .
E.coli O157 is a very serious infection that causes very severe diarrhoea, sometimes with blood in it, abdominal cramps and fever. In children, it can cause kidney failure that can prove fatal.
Anyone who has visited the farm since the beginning of August and has symptoms of E.coliO157 should contact their GP as soon as possible.
“The infection can pass from person to person and so it is important that anyone who is ill should observe strict personal hygiene to avoid spreading the infection.
More top news
Welsh holiday makers have been caught up in travel chaos after British Airlines cancel all flights from Heathrow and Gatwick.
A schoolgirl from Pontypridd is back home after being honoured for her fundraising efforts at a star studded ball in London.
UK terrorism threat reduced just a week before Cardiff hosts the Champions League final.