Danish food safety officials ordered a cleanup and better food handling at Noma, one of the world's top restaurants, after more than 60 people fell ill with viral gastroenteritis from eating at the two-star Michelin eatery that has also hit top spot three times in the world's best restaurants list in Restaurant magazine.

The Danish Veterinary and Food Administration said Friday it had investigated the popular, waterfront restaurant in Copenhagen after complaints from customers who had dined there during a week in February. It was not immediately clear what food had caused the infection.

Agency spokesman Morten Lisby described the outbreak that caused vomiting and diarrhea as "massive."

The 63 infected people ate at Noma between Feb. 12 and 16, according to a food safety report based on an inspection of local restaurants and food retail companies a week later.

Restaurant manager Peter Kreiner apologized for the incidents and said they were trying to track the source of the infection with officials.

"Our business is based on having satisfied customers here and we're incredibly sorry on behalf of our guests," Kreiner told Danish TV2. He said the restaurant had contacted the agency as soon as it became aware of the complaints.

Noma, which opened in 2004, is widely known for its chef Rene Redzepi who relies on fresh, locally-sourced products, from moss and snails to sloe berries and unripe plums. The restaurant has been credited with redefining Nordic cooking and receives thousands of reservation requests every day.

Menus at Noma cost up to 1,500 kroner ($260) and table reservations often must be made months in advance.