Zoom Video Communications temporarily shut the account belonging to a group of US-based Chinese activists after they held an event to commemorate the 31st anniversary of China’s Tiananmen Square crackdown, the activists told Brenda Goh of Reuters on Thursday, June 11, 2020.

Humanitarian China said the event they held on May 31 was hosted by a paid account and was joined by over 250 people worldwide via video-conferencing platform Zoom, while more than 4,000 streamed it on social media, many of whom were from China. The account was shut on June 7, they said in a statement. Humanitarian China founder Zhou Fengsuo said on his Twitter account that the group had yet to receive an answer from Zoom about why its account was closed.

Zoom confirmed the U.S.-based account had been suspended but had now been reactivated. “When a meeting is held across different countries, the participants within those countries are required to comply with their respective local laws,” it said in an e-mailed statement. “We aim to limit the actions we take to those necessary to comply with local law and continuously review and improve our process on these matters.”

The anniversary of China’s bloody crackdown on pro-democracy protests at Tiananmen Square is a highly sensitive matter in China and content related to it is regularly blocked or censored by authorities.