About 400 customers at the restaurant reported feeling unwell
Berkshire's Michelin-starred restaurant the Fat Duck has reopened after a mystery illness among 400 diners led to its closure.
Celebrity chef Heston Blumenthal shut the Bray restaurant at the end of last month after 40 customers fell ill. He said tests ruled out food poisoning.
The council and the Health Protection Agency said "no one source has been identified" but it was "safe to open".
Some test results have yet to come back but the chef said he was "delighted".
"I am delighted the Health Protection Agency and the local environmental health office have given us the all clear to open the restaurant," he added.
"Whilst they are still awaiting outstanding test results we cannot comment further, but obviously we are overjoyed to be able to get back to business as normal."
The Health Protection Agency's (HPA) Thames Valley Health Protection Unit has been working with the Royal Borough of Windsor and Maidenhead's environmental health department to investigate the outbreak of vomiting and diarrhoea.
Samples were taken in the search for the cause of the illness.
A spokeswoman for HPA's Thames Valley Health Protection Unit said: "The agency and local environmental health officers from the Royal Borough of Windsor and Maidenhead consider it safe to reopen as the Fat Duck management has agreed to comply with all the recommendations made after a thorough risk assessment was carried out.
"Results of some tests are still awaited and the detailed questioning of people who reported illness is likely to continue for some weeks in order to build a more complete picture."
Customers leaving the restaurant in the afternoon praised the "fastidious" chef.
Patricia Thacker, 64, from Farnham, Surrey, said: "I was never worried about it and we had heard that he (Blumenthal) was a fastidious chef."