China started blocking the popular photo-sharing app Instagram on Sunday, as part of its moves to squelch any mention of the use of tear gas on pro-democracy protests in Hong Kong.
Instagram, owned by Facebook, had remained one of the few U.S. social networking apps still accessible in a country known for its strict censorship of political topics. But on Sunday, users in China began reporting that the product had been blocked. From Beijing, the app was no longer loading new posts.
In an email on Monday, Instagram said, "We are aware of reports that people are having difficulty accessing Instagram and looking into it."
The Chinese government never comments on why certain Internet products are blocked, only suggesting that they've broken the law in some way. The block on Instagram could be an attempt to stop photos of Hong Kong's pro-democracy protests from spreading into mainland China.
On Sunday, police in Hong Kong used tear gas to disperse large protesting crowds, with video and photos of the clashes immediately going online.
Websites in mainland China have been blocking news about the events, citing the need to follow "relevant legal regulations and policies". Search results for "Hong Kong Tear Gas" have been censored on China's largest search engine Baidu, the site said on Monday.
One of the country's biggest social networking sites, Sina Weibo, has also blocked Chinese language searches for "tear gas". Other news websites in China have pulled down articles covering Sunday's protests.
China's online censorship has been growing stricter this year. In late May, the country began blocking all Google services in the country, cutting access to its search engine, which offered local users uncensored search results.
In July, mobile messaging apps, including Line and KakaoTalk, reported disruptions to their service, at a time when pro-democracy protests in Hong Kong had brought out half a million people.
U.S. social networking sites Facebook and Twitter have long been blocked in the country.