U.K. grocery giant Tesco PLC suspended its supply of Christmas cards from a Chinese factory and said it was investigating a newspaper report that prison labor was used in their production.

All the cards produced by the factory have been withdrawn from sale, Tesco said in a statement on Sunday. If the investigation shows a breach of the company's rule against using prison labor, the factory will be removed from Tesco's suppliers list "immediately and permanently."

The Sunday Times reported earlier that a 6-year-old girl from south London, Florence Widdicombe, discovered a note in her Tesco Christmas cards that read: "We are foreign prisoners in Shanghai Qingpu Prison China. Forced to work against our will. Please help us and notify human rights organization."