Showbiz
Rex Features
The TV chef took the decision to temporarily close the Bray restaurant more than a week ago after 40 people fell ill with symptoms including vomiting and diarrhoea.
However, the BBC reports that that number has now risen significantly and the Berkshire Michelin-starred restaurant will remain closed on Friday.
Blumenthal said that tests had ruled out food poisoning, while sabotage was also not considered probable.
In a statement, the Health Protection Agency (HPA) said that cases reported to the restaurant have risen since media coverage of the story.
The HPA's Thames Valley Health Protection Unit is working with the Royal Borough of Windsor and Maidenhead's environmental health department to investigate the outbreak. Tests have so far proved negative and further investigations are taking place to see if an airborne virus was to blame.
More: Heston Blumenthal, Showbiz
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