The graft inquiry at China Central Television has expanded to a Beijing company co-owned by US public relations giant Edelman and one of its co-founders is cooperating with the investigation, the subsidiary has said. One of CCTV's most recognisable anchors, Rui Chenggang , was taken away by prosecutors earlier this month as part of a wider crackdown at the state broadcaster, which was for decades controlled by a key ally of former security tsar Zhou Yongkang . Zhou is now believed to be the focus of a massive graft investigation. Investigators visited the offices of Pegasus Public Relations Consulting on Thursday, the firm told the South China Morning Post . Edelman in 2007 acquired a majority stake in Pegasus, which was founded by Rui, Steven Cao Gang and Howard Hong Xing. Cao was "cooperating with authorities in the investigation", Pegasus said. He is also the head of Edelman's China arm, the Daniel J.Edelman China Group. Rui sold his remaining 7.9 per cent stake in Pegasus to Cao in 2010. Neither Rui nor Cao could be reached for comment as their mobile phones were turned off. "Relevant authorities visited the Pegasus office in Beijing on July 24. They have asked Pegasus to assist with an investigation," the firm said, adding that it was cooperating. Pegasus confirmed earlier that it counted among its clients corporate sponsors involved in underwriting CCTV's presence at the World Economic Forum in Davos, Switzerland. Rui, who hosts the broadcaster's popular Economic News programme, has been a regular moderator for its coverage of the annual meeting. Edelman was one of the first foreign public relations companies to set up operations in China, and has offices in Beijing, Hong Kong, Shanghai and Guangzhou. The country's top prosecutors announced last month that CCTV's financial news channel director, Guo Zhenxi , and his producer Tian Liwu , were suspected of accepting bribes and had been detained. In December, the mainland's top graft agency said it was investigating Li Dongsheng , a former deputy national police minister who rose through the propaganda ranks during his 22 years with CCTV. Li was widely seen as a protégé of Zhou.