Chinese cyberspace regulators announced on Monday that they have placed the maximum fine allowable on operators of three of the country’s top social media platforms for failing to censor banned content (in Chinese).

All three BAT companies have been affected by the crackdown since the platforms concerned are either owned in whole or part by these companies. Through notices handed by different regional offices, the Cyberspace Administration of China—the cyberspace watchdog—handed maximum fines to the operators of Baidu Tieba, Sina Weibo, partly owned by Alibaba, and Tencent’s WeChat, citing the “failure to fulfill their duties in dealing with pornographic and violent contents” as the reasons.

The fine could be up to RMB 500k ($76k) according to the latest cybersecurity guidelines, although the regulator did not specify the amount for each company.

While the Communist Party Congress is coming up in October, the country has tightened controls over cyberspace: its web crackdown in the past couple of months has been wide-ranging. As early as July this year, China has strengthened curbs on VPN. The pressure continued to accumulate over the summer and peaked when Apple removed VPN apps from China App Store.