China has in recent weeks widened existing curbs on the use of iPhones by state employees, telling staff at some central government agencies to stop using their Apple mobiles at work, two sources familiar with the matter said. One of the sources said they had not yet been given a deadline to cease their iPhone use. Apple and China's State Council Information Office, which handles media queries on behalf of the government, did not immediately respond to requests for comment. Bloomberg on Thursday reported that China planned to broaden the ban to state firms and agencies, citing sources. China has increasingly emphasized using locally made tech products, as technology has become a major national security issue for Beijing and Washington.