Conran's London restaurant Quaglino's was at the centre of an immigration sting last week which saw five staff arrested.
The raid, at 6pm on Wednesday (11 January), followed a tip-off from immigration officials about illegal workers and forged immigration documents.
Conran said an investigation was taking place into the personal documentation on some of Quaglino's foreign national employees, but the company had been cleared of hiring workers illegally. "It has been established that Quaglino's has followed all the requisite controls and procedures," said a spokeswoman.
A Home Office statement said: "Four workers were arrested as suspected immigration offenders by the immigration service and have been detained pending further enquiries. A further man was arrested on behalf of the Department of Work and Pensions."