China has arrested over 15k individuals as part of its new program to ‘clean the internet’ of criminal activity.

On Tuesday, Chinese police announced the detentions, which they said were the result of crimes that “jeopardized internet security.” Police declined to specify over what time period these individuals had been clapped in irons but a statement on the Ministry of Public Security’s website suggested the bulk of the arrests were made in recent months.

The Ministry said police had investigated 66k websites, exposing 7,400 cases of ‘cybercrime.’ In addition to sites providing “illegal and harmful information,” police were focusing their efforts on sited promoting pornography, explosives, firearms and gambling.

The timing of Tuesday’s announcement appears at least partly intended to stifle online criticism of the government’s response to last week’s chemical warehouse explosion in Tianjin. China’s ‘great firewall’ is renowned for its army of online sentries keeping watch over things upon which the government frowns, particularly information spread via China’s popular social networks.