One of the last Western social media apps available in China, Signal, has now gone dark in the nation, according to reports from TechCrunch and Reuters. The encrypted app, often used by reporters and others needing ironclad privacy, has been unavailable in mainland China since early this morning. Signal’s website, meanwhile, was blocked in the nation on March 15th. 

TechCrunch notes that Signal is still available for download on Apple’s App Store in China, meaning the government hasn’t ordered Apple to remove it, and it can still be used via a virtual private network. The app has been installed over 500,000 times in the nation — a pittance compared to the 1.1 billion users of China’s dominant messaging app, WeChat — but it’s still a significant number given China’s strict internet laws. The government blocked other popular social media apps like Facebook, Twitter and Instagram years ago. 

Signal’s popularity has surged recently around the world, particularly after WhatsApp updated its terms to allow parent Facebook to share user data. The app has stopped working in China before without a VPN only to resume running again, Reuters remarked, so it’s not clear if the current outage will be permanent.