An investigation is continuing into a possible link with a Wrexham fish bar
Four people who became ill after an E.coli outbreak have the same strain of the bug, tests have shown.
The National Public Health Service for Wales (NPHS) said all four cases in Wrexham were confirmed as E.coli O157 phage type 2.
Karen Morrisroe-Clutton, 32, is in intensive care and three-year-old Abigail Hennessey, is in hospital. Two women are recovering at home.
The Llay Fish Bar, Llay, is closed while a possible link is investigated.
In a statement, Dr Judy Hart, of the NPHS, said: "Laboratory testing has now confirmed all four cases as E. coli O157 phage type 2.
"This suggests that they are all part of the same outbreak and their illness is linked. Further tests will now be conducted to confirm whether the samples from the four cases in Wrexham are absolutely identical.
"It is important to stress that as the investigation continues, we are examining all possible sources of the illness including foreign travel, agricultural and leisure activities, as well as food and water consumed before the beginning of illness."
She said no new cases have been confirmed and it is believed the incident which caused the food poisoning occurred a few weeks ago.
Jeff and Sarah Hennessey, from Wrexham, said their daughter Abigail was on dialysis for five days, but was now off the machine, recovering at Alder Hey Hospital in Liverpool and "eating and drinking quite well".
Both Abigail and her mother ate at the Llay Fish Bar, but cannot be sure they picked up the infection there.
Karen Morrisroe-Clutton, from Wrexham, also ate food from the chip shop, and remains "seriously ill" at the town's Maelor Hospital.
Her mother has criticised Wrexham council after its inspection of the premises a year ago found poor hygiene conditions.
The inspection also found major non-compliance with food legislation and the authority gave its lowest possible star rating of zero stars.
Pierre Bartlett, the solicitor for Ramazan Aslan, the owner of the fish bar, said his client was co-operating fully with the investigation and his thoughts were with the families of those who are ill.