When Xinhua News Agency broke the story on Zhou's investigation, it quickly went viral online. The news of the investigation came alongside an announcement that the Party will hold the Fourth Plenary Session of the 18th CPC Central Committee in October to discuss key issues concerning the promotion of the rule of law.

"Announcing Zhou's case now is part of the preparations for the Fourth Plenary Session. The results of his investigation could be written in the documents reviewed by the meeting," said Li Chengyan, a professor at the School of Government of Peking University.

Until Zhou, only four members of the Political Bureau of the CPC Central Committee have been investigated for graft since the reform and opening up started in the late 1970s. They were former Beijing Party chief Chen Xitong, former Shanghai Party chief Chen Liangyu, former Chongqing Party chief Bo Xilai and former Vice Chairman of China's Central Military Commission Xu Caihou.

Standard procedures have been followed during the investigations against these top Party leaders. The CCDI, which is in charge of the investigation, will hand over a report on its conclusions to the Political Bureau of the CPC Central Committee for review. The political bureau will then decide whether or not to remove Zhou from all Party and government positions. After this, if Zhou is proved guilty, he will be dismissed from the public service, stripped of Party membership and transferred to judicial organs for prosecution.

The People's Daily commentary said that there is no member in the CPC who is above the Party's discipline, adding that officials and Party members will eventually pay the price if they unscrupulously pursue selfish ends or abuse their power.

It also calls for efforts to enhance the sense of Party spirit, fortify the belief in the Party and strictly enforce the Party discipline among the CPC members.

Last October, Zhou visited the China University of Petroleum's 60th anniversary celebration as an alumnus. It was the last time he was seen in public.

Family ties

With a formal investigation against Zhou being suspected for a long time, Party disciplinary authorities had been tightening the net for more than a year. A large cohort of Zhou's one-time aides and proteges have been investigated since December 2012, including former Party and government leaders of Sichuan, former senior managers of the CNPC and a former minister of the State-owned Assets Supervision and Administration Commission.

Zhou was also considered a patron of disgraced Chongqing Party chief Bo Xilai, who was convicted last year and is serving a life sentence for corruption, embezzlement and abuses of power.

Many of Zhou's family members were also suspected of leveraging Zhou's influence to amass their extraordinary wealth. Those investigated included his brother Zhou Yuanqing; his second wife, Jia Xiaoye; and various in-laws. On the same day Zhou's investigation was announced, Chinese news magazine Caijing broke the news that Zhou's eldest son Zhou Bin had been arrested by prosecutors in Yichang, central China's Hubei Province, on the charge of being involved in "illegal business operations."

Reports by different Chinese media outlets have detailed how Zhou Bin, 42, built a business empire in oil and real estate through connections that were not explicitly stated but that clearly hinted at Zhou. Another news magazine, Caixin Century Weekly, reported in its online edition that Zhou Bin and his wife owned properties in Beijing that were valued as worth more than 130 million yuan ($21 million) in 2012. Zhou Bin has also been reported as participating in trading the rights to the state-owned oilfields for his own gain.

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