About 40 customers at the expensive restaurant fell ill
Chef Heston Blumenthal says tests have ruled out food poisoning after up to 40 customers reported feeling unwell.
He shut down his Michelin-starred restaurant the Fat Duck, in Bray, Berkshire, last Tuesday and called in environmental health officers.
The entire menu was tested but all results proved negative. Final tests are being carried out to see if an airborne virus caused the sickness.
Blumenthal said he hoped the restaurant would reopen by the end of the week.
The chef told the BBC: "It has been awful. We have done our own food testing for the last four years.
I don't want anyone leaving with a headache let alone feeling unwell
"Everything is tested from the food coming out of the ground, from the farm into the kitchen and to the customer.
"When we started getting telephone calls we took it very seriously.
"I don't want anyone leaving with a headache let alone feeling unwell."
He decided to close the restaurant as some of the results took up to a week to come back.
"We've had staff tested, some customers tested and so far it is categorically not food poisoning," he added.
"We are now looking at the possibility of an airborne virus.
"This could have come from a customer, a staff member not showing symptoms or from outside the restaurant.
"A customer called me to say they came in with a table of four, three of them got ill, but then their children got ill so they are convinced it is a virus."
Environmental health officers from Windsor and Maidenhead Borough Council are carrying out their final tests, which include looking for signs of a virus.
The chef has so far had to cancel more than 500 bookings.
Diners at the Fat Duck - one of only three restaurants in the UK with three Michelin stars - can experience dishes such as snail porridge or sardine on toast sorbet.
But they need to book months in advance to secure a table at the restaurant, where the tasting menu costs £130 .