Experts fear the number of cases - currently standing at 115 - could increase. The majority of the current cases are among schoolchildren from 32 schools across four health authority areas.
FSA Wales is advising any food businesses that have received cooked meat from John Tudor and Son to withdraw it from sale immediately and to contact their local authority, although there has been no conclusive evidence that Tudor's was the source of the infection.
Nonetheless, the agency has now asked all local authorities in Wales to contact any small to medium-sized caterers, local shops, delicatessens and pubs, to make sure they have not bought any cooked meat from Bridgend supplier John Tudor. The company said that it was co-operating fully with investigators.
But for parents of children affected by the outbreak, this is not good enough. Four children with acute kidney problems are currently being treated in hospitals in Liverpool and Bristol, and 25 people - mostly children - have been admitted to hospital in the past week.
Parents are now calling for a public inquiry.
Health Minister Dr Brian Gibbons said an inquiry would be held, but did not specify whether it would be a full public inquiry. First minister of the Welsh Assembly Rhodri Morgan however hinted that a full public inquiry was a possibility.
"There is no difficulty about having to make this as open and as independent and as transparent as possible," he told the BBC.
"I can't give you the details of the inquiry now, but simply a commitment that it will be an open inquiry, because the lessons must be learned."
E. coli O157 causes food poisoning and sometimes kidney failure when people eat undercooked meat. European consumers have become increasing concerned about food safety, mainly due to the bovine spongiform encephalopathy (BSE) scare in cattle beginning in the late 1980s, a foot and mouth disease outbreak in 2001 and of avian flu in 2003.
Consumer concerns have in turn led to tougher regulatory action and increased surveillance of food safety.