Tests have been carried out on the water supply at a special school in Blackpool after children there began falling ill.
Public health officials say youngsters at Highfurlong School in Blackpool Old Road are 'likely' to have contracted a virus such as the highly-contagious norovirus after reporting bouts of sickness and diarrhoea, but said investigations are still underway.
United Utilities said it had taken samples of the water supply and 'found nothing that would cause illness'.
MORE OF TODAY'S TOP STORIES
"We have advised the school that it would be sensible to carry out an inspection of the internal plumbing to make sure their system meets the required water fittings standards which are designed to protect water quality," a spokeswoman said.
Mark McGivern from the Cumbria and Lancashire Health Protection Team said officials were working with environmental health officers and the council's health and safety team to 'investigate the incident and ensure measures are in place to prevent the spread of illness'.
He added: "At this stage it's not possible to pinpoint exactly the source of the illness and further investigation is ongoing. We have asked the school to report cases of illness to us as part of this investigation to help confirm the cause of the illness."
A letter purportedly sent to parents by Highfurlong headteacher Rosie Sycamore, which was posted onto social media, said: "Public Health England has requested details of any pupils or staff that experienced sickness in recent weeks.
"I will be collating this information, which includes names, addresses and dates of birth, symptoms, and duration of illness.
"This information will be forwarded to Public Health England by the end of school on Friday, 27th October, 2017.
"Bottled water will be continued to be used throughout the school for drinking purposes until further notice."
The school has around 50 children on its books, its last Ofsted report said.
Public Health England said it received ‘over 40 reports of illness in staff and children over the past few weeks’, but said ‘this isn’t a particularly high number for norovirus’.
Coun Graham Cain, the cabinet member for resilient communities, added: "Obviously, we understand that parents will be concerned. Parents have been contacted by the school by letter and text to advise them of the situation.
"With any potential risks to health, it is important that they are investigated fully. Blackpool Council has been working closely with all the relevant organisations and all precautionary measures have been put in place, such as the provision of bottled water.
“On the basis of the investigation to date, there are no significant concerns over and above those associated with seasonal diarrhoea and vomiting illnesses.
"However this will be continually reviewed in the light of any new information.
“The school is now closing for half term and we will use that time to further assess the situation and will provide further updates as they become available.”
The special school shares an entrance with Aspire Academy, where pupils are currently on their half-term break, after moving into its new £14m premises in November 2015.
John Topping, spokesman for the Fylde Coast Academy Trust (FCAT), which runs Aspire, said: "United Utilities has been conducting tests on water in a variety of areas, which includes Aspire Academy, and nothing untoward was found.
“Any member of staff working in school during the half-term has been advised to use bottled water as a safety precaution.”
Public Health England said people with signs of the norovirus, which is easily transmitted and airborne, should stay away from school, work, or university until they have been symptom free for 48 hours.