The boss of Byron restaurant says he has not been able to contact two waiters who were on shift when teenager Owen Carey died from an allergic reaction.
Speaking to ITV News Simon Wilkinson said the company had no phone number for the former staff members and they didn't respond to emails.
One of them may have served Owen Carey who died after eating grilled chicken with buttermilk which wasn't listed as an ingredient on the menu.
Byron said it only found out about the case 11 months after Owen visited the restaurant.
Mr Wilkinson said he wasn't worried the waiters could still be serving customers in other restaurants.
A coroner ruled Owen Carey was misled into believing there were no allergens in his meal at Byron.
The teenager suffered a fatal reaction after eating grilled chicken coated in buttermilk at the restaurant at the O2 Arena in Greenwich in April 2017 while celebrating his 18th birthday.
The family of Mr Carey have called him their "shining light" and are calling on the Government for 'Owen's Law' to force restaurants to have clear information about allergens on each individual item on the menu.