President Xi Jinping has set up a special unit headed by a senior policeman and deputy minister of public security to investigate the scandal surrounding retired leader Zhou Yongkang, bypassing the Communist Party's internal disciplinary apparatus, sources say. Beijing police chief Fu Zhenghua will report directly to Xi, according to police and graft watchdog sources. Fu is the first person in the party's history to also hold the concurrent posts of head of Beijing's armed police, the Standing Committee member of the party's Beijing municipal committee and deputy minister of public security. The arrangement is unusual and reflects not only the sensitivity of Zhou's case but also Xi's personal interest in it. Corrupt officials are usually dealt with by the party's Central Commission for Discipline Inspection (CCDI) and kept incommunicado in an extra-legal, internal system of detention called shuanggui for interrogation before being handed to police and prosecutors. But at least three separate sources with knowledge of recent interrogations widely believed to be part of a larger corruption probe into Zhou's affairs said police were taking the primary roles in these cases. It is believed that Xi and CCDI head Wang Qishan wanted police who are more experienced with criminal investigations to handle the investigation rather than the CCDI, whose abilities and methods have been questioned recently. One of the sources said the top leaders were not satisfied with the CCDI's working style and were aware of frequent abuses during inquiry processes. But it remains unclear if the new practice of having a special team headed by a senior policeman would set a pattern. "Many of the CCDI officials have been transferred from other departments and have very little experience of investigations and crime-solving," the source said. "Xi and Wang agreed to use police to lead the probes as they believe the police are more professional." Another source, quoting CCDI officials and police, said: "Xi entrusted Fu to co-ordinate the recent inquiries related to Zhou, while Wang is overseeing the cases and anti-corruption operations in general. Fu is leading a small group of police, mostly from the Beijing Police Bureau, to probe cases such as those of Wu Bing and Guo Yongxiang ." Wu, a Sichuan billionaire widely believed to have close ties with associates of Zhou's family, was seized in Beijing in early August. Guo, a former deputy governor of Sichuan who rose through the ranks as Zhou was promoted, was detained in June for "serious disciplinary violations" - a party euphemism for corruption. Fu, 58, was only promoted to deputy minister post in August after the retirement of Zhou, the former national security chief who ruled over the police and other law enforcement agencies for nearly a decade. Fu is also leading a controversial crackdown on influential commentators on the internet, a prominent plank in Xi's plan to "seize the ground of new media". A forensics expert, Fu made his name with the high-profile bust of Beijing's Passion Nightclub months after he was named the city's police chief in 2010. The massive crackdown on several prostitution operations, including the luxurious club, surprised the public as the club owner was regarded as being well-connected to military officials. Another source confirmed the shift to relying more on police than the CCDI in the Zhou case, adding: "Guo Yongxiang was arrested in Chengdu by police from Beijing." The source added that at a time when the leadership was calling for greater rule of law, it was important that a special unit investigated corruption cases to avoid the much-criticised shuanggui system. Under party regulations, discipline inspection units can hold suspects under shuanggui for up to four months. But in reality detention is indefinite and reports have emerged of party members being tortured and even beaten to death. The first source said a series of "bold reforms" of CCDI was expected to be announced after the party's keynote meeting next month. Authorities endorsed the decision to probe Zhou at the secretive annual party meeting held in August at the Beidaihe resort in Hebei , the Post reported earlier. No Politburo Standing Committee member - retired or sitting - has been investigated for economic crimes since the end of the Cultural Revolution in 1976. Several of Zhou's former aides are now under shuanggui, including Jiang Jiemin , ex-chairman of the China National Petroleum Corporation, and Guo, who worked alongside Zhou for 12 years until 2002.