London ? Chef Heston Blumenthal and health officials say a virus may have caused an outbreak of illness among diners at England’s Michelin-starred Fat Duck restaurant.

The restaurant was closed for more than two weeks starting Feb. 24 after scores of diners were struck by bouts of diarrhea and vomiting. Initial reports said 40 diners had fallen ill, but the Health Protection Agency said Friday that 529 people have now reported becoming sick after eating at the Fat Duck.

Blumenthal was quoted by Australia’s Hospitality magazine as saying several members of staff and customers had tested positive for norovirus, an easily transmitted bug known as “winter vomiting” disease.