LONDON — The audio-only social media app Clubhouse appears to have been blocked in China.

Queeny Li, a communications professional based in Shenzhen, and Michael Norris, a tech analyst in Shanghai, told CNBC that the Clubhouse app no longer works for them.

“Clubhouse has been blocked,” said Norris, echoing what multiple media reports have said.

“Clubhouse’s ban was expected,” Norris added. “Indeed, the sudden rush to give Clubhouse a whirl was driven by the sense that a ban was imminent.”

Some Clubhouse users in China are now being shown an error message when they open the app. The message reads: “An SSL error has occurred and a secure connection to the server cannot be made.”

U.S.-based Clubhouse, the Ministry of Foreign Affairs of the People’s Republic of China and the Chinese embassy in London did not immediately respond to a CNBC request for comment.

The invite-only discussion app, which lets people chat with their voices instead of written messages, has boomed in popularity over the last few months.

It initially gained traction with the Silicon Valley tech community, but in recent weeks the app has been downloaded onto smartphones across China.

While the iPhone app is not available to download from the Chinese App Store, people in China were able to get it by using overseas Apple IDs.

Chinese ecommerce sites have been selling thousands of Clubhouse invites for up to $77, according to The Financial Times.

Clubhouse, which is valued at around $1 billion and boasts over 2 million users, worked for people in China that managed to download the app and obtain an invite up until Monday, when the apparent block came in.

Unlike other apps, Clubhouse was not censored by the Chinese Communist Party and users were free to talk about whatever they pleased.

Chinese authorities have blocked U.S. social media apps like Facebook and Twitter, and internet search results are censored by the government. The country’s digital censorship of overseas platforms has been dubbed the “Great Firewall.”

Meanwhile, the U.S. government has been clamping down on Chinese tech firms like Huawei and TikTok over the last few years.

“At one level, China is cracking down on any technology that challenges how the government controls society,” Abishur Prakash, a geopolitical specialist at the Center for Innovating the Future (CIF), told CNBC.

“This is nothing new,” he added. “But, at another level, China is rapidly ‘unplugging’ from U.S. technology, even the new platforms and services. This is further driving the split between the U.S. and China.”