Four children with E.coli are being treated in hospital as the number of cases in the south Wales outbreak rose again to 115 across 32 schools.
A boy of four from the Cynon valley, was airlifted to Alder Hey Hospital, Liverpool on Saturday night.
A boy and girl, both nine, are also in a stable condition in Alder Hey. A girl of three is "satisfactory" in Bristol.
New figures on Sunday showed 25 people, mostly children, have been admitted to hospital in the past week.
The parents of one victim have asked solicitors to press for the official inquiry to be urgent and open.
The Alder Hey spokeswoman said a boy and girl with E.coli had been responding to treatment and some improvement had been seen in another boy admitted several days ago.
The outbreak control team said more of the new cases were acquired within families and from people who had eaten cooked meat from premises other than schools.
Officials warned a further rise was likely, but not because the outbreak was still "live". They said the bacteria sometimes took more than a week to incubate.
Boy, 4, of Cynon valley, flown to Alder Hey from Prince Charles Hospital, Merthyr, on Saturday.
Garyn Price, 9, of Aberdare, flown to Alder Hey on Monday.
Maria Griffiths, 9, of Pontypridd, had surgery in Alder Hey on Tuesday.
Caitlin Bray, 3, of Rhondda, being treated in Bristol. Her brother Thomas, 4, and mother Lisa also treated in Llantrisant.
Daniel Sacchi, 11, of Bridgend, returned home on Thursday.
The latest schools with infections are Ynyswen Infants, Treorchy, Rhondda Cynon Taf, and Cwrt Rawlin Primary, Caerphilly, while Hawthorn Primary, Pontypridd, was added on Sunday.
Health Minister Brian Gibbons announced on Friday that an inquiry would be held into the food poisoning in the Rhondda Cynon Taf, Merthyr Tydfil, Bridgend and Caerphilly areas.
It has been linked to Bridgend meat supplier John Tudor and Son. The Food Standards Agency has told any business which received cooked meat from the company to withdraw it immediately and contact their local authority.
The FSA has also asked all local authorities in Wales to contact any businesses to ensure they have not bought any cooked meat from the firm, to ensure it obtains a full list of Tudor's customers.
Sunday: Seven linked cases confirmed by Rhondda Cynon Taf and Merthyr councils.
Monday: Cases rise to 23 and officials warn of further rise.
Tuesday: Cases rises to 41 in 19 schools as school canteens ruled out as source.
Wednesday: 56 cases in 25 schools and outbreak linked with Bridgend food supplier John Tudor and Son.
Thursday: Cases up to 68 as health officials move to quell public fears.
Friday: Official inquiry ordered; cases reach 75.
Saturday: Parents call for inquiry to be fully public; 108 cases in 31 schools.
Sunday: First Minister Rhodri Morgan pledges transparent inquiry; 115 cases in 32 schools.
Officials have said there is no conclusive evidence that Tudor's is the source of the infection. The company said it had had no previous hygiene problems and is co-operating fully with investigators.
An emergency prohibition order has been taped to the company's premises instructing the firm to stop trading.
The notice said a court was satisfied there was evidence to show "an imminent risk of injury to health" from "unsanitary condition of the premises resulting from inadequate disinfection procedures".
It said a "vac packing process which allows cross-contamination" was "in an unclean condition and which is located underneath the electronic fly-killer".
Primary: Abertaf; Blaengwawr; Bedlinog; Pengeulan; Capcoch; Caradog; Upper Rhymney; Comin; YGG Llwyncelyn; Cwmdare; Aberdare Town Church School; Troedyrhiw; Rhigos; Glenboi; Maesycoed; Cwmlai; Hirwaun; Parc Lewis, Ysgol yr Castell; Brynna; Cwrt Rawlin, Hawthorn.
Infants: Cwmbach; Penygraig; Cynon; Glyntaf; Ynyswen.
Secondary: Pen y Dre; St John the Baptist; Archbishop McGrath; Ysgol Pen Yr Englyn; Treorchy.
Stephen Webber, of solicitors Hugh James, said the parents' priority was that children recovered, but legal action may follow.
Mr Webber said parents generally were worried about what had caused the outbreak, which has mainly affected children.
"The main concern is that there is a full public, open inquiry to find out what's happened, why it's happened and to stop it happening again."
Prof Hugh Pennington, who chaired an inquiry into Britain's worst outbreak of the same strain, E.coli 0157, in Lanarkshire in 1996, has suggested that the new inquiry could investigate prepared food that would not be cooked.
Seventeen people, mostly elderly, died and about 500 were affected in the Scottish outbreak, which was traced to a butcher.
Prof Pennington told BBC Radio Wales that E.coli would be killed by cooking raw meat, "but if you get the bug onto prepared food that isn't going to be cooked clearly that is a way of people eating the bug and falling ill.
"And that's one thing I would suspect is going to have to be looked at in detail," he added.
"We've been fighting this particular kind of problem in food preparation for many years and we are still not quite on top of it."