China said the case of a Wells Fargo & Co. banker blocked from leaving the country was related to a criminal matter, escalating an episode that already underscored global firms’ fears about operating in the nation.

China's Foreign Ministry said on Monday that Chenyue Mao, the Wells Fargo banker who has been blocked from leaving the country, was involved in a criminal case and obliged to cooperate with the investigation.

An Atlanta-based banker working for Wells Fargo has been prevented from leaving China, the latest incident that threatens to amplify concerns among Western executives about the potential consequences of visiting the world’s second-biggest economy.