Internet authorities have ordered the mainland's leading search engine operators to purge 'harmful information' on the internet amid an intense crackdown on critical online voices ahead of the 17th Communist Party Congress to be held next month. The Ministry of Information Industry said it had approached eight major operators, including Google, Baidu, Yahoo, Sina and Sogou, on Wednesday to tell them to delete offensive and banned online content. The companies were ordered to 'provide healthy and positive internet search services and to enhance online civilisation' by reorganising their administrative systems and removing problematic content. Yahoo China spokesman Xu Yang said an inspection team from the ministry would visit the operators, including Yahoo China, to monitor the progress of the campaign after one week. Internet authorities have been cracking down on online pornography since April. However, the search engine companies were ordered more broadly to remove all 'harmful information'. Mainland internet regulations categorise harmful information as that which could 'endanger state security, leak state secrets, overthrow the government and spoil unity'; 'damage state honour and interests, incite national hatred, discrimination'; 'violate state religion policies and promote cults'; spread rumours; disturb the social order; and spread pornography, gambling or violence. The definition of 'harmful' also includes any information that incites actions forbidden by laws and regulations. A senior industry source, who did not want to be named, said the purpose of the crackdown was to 'suppress critical opinions and dissenting voices in cyberspace before the 17th party congress, rather than to purge pornography'. He said censors had never been determined to stamp out the rampant pornography on the internet, but were now keen to silence critical voices. 'As entry points into cyberspace, it's much easier to administer search engines and get them to block harmful information,' the source said. An increase in raids on internet service companies during the past few weeks had aroused unease in the industry before Wednesday's order to the leading search engine operators, he said. Shantou Telecom was ordered by authorities on Wednesday to suspend 2,000 local servers because some of its clients' bulletin boards and websites carried banned posts. Forty of the servers were permanently shut down. A Guangzhou-based blog service, www.AnyP.cn , was closed last month for carrying banned information. The company claimed on its website that it was 'ordered to undergo thorough content censorship by supervising authorities'. Mr Xu, the Yahoo China spokesman, said he was instructed to 'arrange special staff and have enough technical support to fulfil the task'.