Food poisoning at Noma, a Danish restaurant often hailed as the world's best, has left over 60 people suffering from vomiting and diarrhoea.

Health officials said diners at the two Michelin-starred venue in Copenhagen fell ill over a five-day period in February.

It was not clear what caused the food poisoning, but reports say the source may have been a sick kitchen employee. Diners fell ill with what is known in Denmark as Roskilde virus, the Copenhagen Post reported.

Noma, which topped Restaurant Magazine's list of the world's 50 Best Restaurants in 2010-12, has apologised, after Danish food authorities found that poor hygiene in the kitchen was to blame for the outbreak.

The agency, Fødevarestyrelsen, wrote in its report: "There has been illness among staff who have handled the food product. The inspection visit was due to guests complaining of vomiting and diarrhoea."

Agency spokesman Morten Lisby was quoted as describing the outbreak as "massive", according to the Associated Press news agency.

Noma was also criticised for not disinfecting its kitchen quickly enough to prevent the virus from spreading. There was also no hot water in the taps that staff used to wash their hands.

Noma acknowledged that internal procedures had not been good enough and that an e-mail from an employee reporting his sickness had not been seen in time.

The managing director, Peter Kreiner, said: "Since the outbreak we have worked closely with the health authorities to get to the bottom of it and find the source of infection.

"We are extremely sorry about all of this and I have personally been in dialogue with all the guests who were affected and discussed compensation for them." The restaurant would not be closing down, he added.

Noma charges up to £175 for a menu without drinks, and reservations are often made months in advance. Despite having only 40 covers a night, it receives around 100,000 booking enquiries a month.

Last year, Noma set up a pop-up restaurant at Claridge's hotel in London, offering a nine-course degustation menu at £195 a head that included beef tartare with sorrel, juniper salt and tarragon cream - and live ants.

A food poisoning outbreak at Heston Blumenthal's Fat Duck restaurant in Bray, Berkshire, nearly three years ago was the biggest linked to norovirus contamination at a restaurant yet recorded, according to a report published in the journal Epidemiology and Infection.

At least 240 people fell ill with gastroenteritis-like symptoms such as nausea, vomiting and diarrhoea, in an outbreak that caused the temporary closure of the restaurant. Contaminated oysters and handling of food by infected staff were said to be the likely causes.

"The size and duration of this outbreak exceeded any other commercial restaurant-associated norovirus outbreaks in published literature. It is hoped that lessons learned from this outbreak will help to inform future action by restaurateurs, especially in early notification to public health authorities once an outbreak is suspected.

"It is also notable that diners may often choose to inform restaurants directly rather than their doctors or public health authorities. It is important that both diners and restaurants are provided with better information about whom to inform and when to inform once an outbreak of illness is suspected," said the report.