Beijing, Mar 16 (IANS): Encrypted messaging app Signal on Tuesday was no longer working in China without the use of a virtual private network (VPN).

According to reports, the app, which is used for encrypted conversations, is currently unavailable in mainland China.

The website of the app has been banned in mainland China since March 15, according to censorship tracking website Greatfire.org.

The Chinese government has not made any announcement about Signal being blocked or banned in China, but Signal's website was unavailable in the country, reports TechCrunch.

However, the app was still available on Apple's China app store and both the app and the website appeared to be working normally in Hong Kong.

As per, data company Sensor Tower, Signal had been downloaded close to 510,000 times on iOS in China and has been downloaded 100 million times worldwide on the App Store and Google Play combined.

Signal's growth was likely concerning for Chinese authorities who attempt to monitor and control everything done on the internet in mainland China.

The app has also seen a significant growth in the India market.

Executive Chairman of Signal Foundation Brian Acton, who co-founded WhatsApp with Jan Koum before selling it to Facebook CEO Mark Zuckerberg for $19 billion, aims to add 100-200 million users on Signal in India over the next two years.

Acton left WhatsApp in September 2017 to start the Signal Foundation, dedicated to helping people who have access to private communication through an encrypted messaging app.