Social media app Clubhouse has been blocked in China from Monday evening following a series of chats that were deemed politically-sensitive. The app is a platform for uncensored audio conversations and allows thousands to listen in.

Reports of mainland China users being unable to log began to emerge at about 7 p.m. Invitations to join the invite-only service that had been selling on e-commerce platform Taobao were also taken down, according to Hong Kong’s Apple Daily.

Some users said they could still access the platform’s chat rooms if they used a virtual private network to jump China’s so-called Great Firewall. VPNs are illegal for most users in China and the Apple-only Clubhouse app was not available in China’s iOS App Store.

Clubhouse was launched last year, but went viral only recently after Elon Musk appeared on a chat. Chinese-speaking users flocked to the app, and away from the usual censorship, many used it to engage in politically sensitive conversations about Uyghur concentration camps, the 1989 Tiananmen crackdown and the national security law in Hong Kong. Some of the chats exceeded the limit of 5,000 users.

A number of chat rooms saw direct exchanges between users from mainland China, Taiwan and Hong Kong, who previously lacked the opportunity to communicate directly in an uncensored format.

Conversations ranged from political debates over freedom and democracy to the Chinese government’s policy of prioritizing economic development.

The move to have Clubhouse “walled” was a largely expected outcome, said some users, who seize the opportunity of expressing themselves while the opportunity lasted.

The app also attracted a number of celebrities from the region to host live chats.