Following reports that the Chinese government has barred government workers from using iPhones or any other foreign electronic devices for official government functions, and even forbid bringing them onto government grounds, Apple’s market value plummeted almost $200 billion.

On Thursday, Apple shares fell almost 3%, leaving them down by 6.4% over the last two days. In addition the stocks of several of the tech giant’s major suppliers have also taken nosedives. TSMC, the Taiwanese chipmaker which holds the title as the world’s largest contract chipmaker, and a major supplier of Apple, saw its shares fall more than 2%, as ASE Technology Holding, among the largest semiconductor testing and packaging companies in the world saw its shares fall 2%. Largan Precision, a major manufacturer of camera lenses, saw its shares fall over 3%.

According to Allen Huang, executive director of Mega International Investment Services Corp in Taipei, investors fear that China may further expand those curbs on the use of phones by officials. As the largest foreign market for Apple products, with sales in the country accounting for roughly a fifth of the company’s revenues, the effects on the company could prove broad-reaching.

Some agencies had already barred their employees from using iPhones for years, however the latest government rule has significantly expanded the policy throughout government.

Beijing had previously demanded in February that multinational companies which operate in China, such as Apple, Amazon, and JPMorgan Chase, must undergo an audit of their data-handling policies before they would be allowed to send any locally generated data outside the country.

Meanwhile in the United States, government officials have long been banned from using phones from Chinese companies such as Huawei, or from downloading Chinese apps like TikTok’s social media app to any government-issued devices. Officials have expressed concerns such devices and apps could compromise a security risk, and give access to user data to China.