Quarry Bank Mill is currently closed until further notice due to a high level of staff illness.
Public Health England North West's Cheshire and Merseyside health protection team and Cheshire East Council are investigating an outbreak of diarrhoea and vomiting linked to Quarry Bank which has been reported by a number of National Trust Employees.
A spokesperson for the National Trust said "Due to a high level of illness among National Trust staff we have made the decision ourselves to close Quarry Bank and investigations are underway into what has caused it. At this stage it's not possible to pinpoint the exact source of the illness, or determine whether it originated at Quarry Bank.
"We are working closely with the local environmental health officer to support them in their investigations. We want to do all that we can to look after our visitors, staff and volunteers, and while we understand people will be disappointed by the closure, we won't reopen until we are completely satisfied that everything is back to normal."
Rita Huyton, Acting Nurse Consultant from PHE's North West Centre, said: "We are working closely with a number of local partners to establish the cause of the illness. At this stage it's not possible to pinpoint exactly the source of the illness, or determine whether it originated at Quarry Bank, and further investigation is ongoing. The National Trust at Quarry Bank took the decision to close the property as a precaution. We are working with the management team at Quarry Bank and a number of other partners who are fully supporting the investigation.
"Generally, people who have symptoms of diarrhoea and vomiting should stay away from school, work or university until they have been free of symptoms for 48 hours. Everyone should be encouraged to practice good hand hygiene and wash hands thoroughly and regularly at all times, but particularly after using the toilet and before eating."
The National Trust does not anticipate the site in Styal will reopen until Saturday, 9th March, at the earliest.