China is reining in one of its most successful tech businesses just days after its US IPO

China’s cybersecurity regulator has ordered all app stores in the country to block downloads of Didi Chuxing, China’s biggest ride-hailing app. The Cyberspace Administration accused Didi of improperly collecting and using its customers’ personal data.

For now, the app’s existing 600 million users and drivers customers can continue using Didi normally, so long as they have already downloaded the app. But new customers will not be able to start using the service until the company addresses the regulators’ data concerns.