Zhou Yuanqing, brother of a former senior official, and his wife, Zhou Lingying, were put under investigation in December 2013 under suspicion of using their government connections to amass wealth, according to media reports.

After a string of cases, it has been revealed that people close to Zhou Yongkang, former member of the Political Bureau Standing Committee of the Communist Party of China (CPC) Central Committee, were allegedly involved in corruption. 

Officials told The Beijing News that Zhou Yuanqing, former head of the land and resources bureau in Huishan district of Wuxi in Jiangsu Province, and his wife were investigated due to their ties with companies affiliated with China National Petroleum Corporation (CNPC), where Zhou Yongkang served as a senior official from 1988 to 1998.

A company controlled by Zhou Lingying jointly founded a new company with Kunlun Energy Company under CNPC in 2012. This then expanded into the natural gas business using her relationship with CNPC.

Li Hualin, chairman of the board of Kunlun and vice general manager of CNPC was investigated in 2013 for seriously violating discipline.

Zhou Lingying's company, set up in 2010, was granted the sole license to sell Audi vehicles in Jiangyin, Jiangsu Province soon after the company's launch. Audis are deemed to be the vehicle of choice for Chinese officials, Caixin magazine reported Monday. Sources said that obtaining such a license needs solid connections with officialdom, and even senior Audi management cannot intervene, the report said.

The report said that Zhou Yuanqing's relatives also earned money from helping others to smooth out issues using their connections, such as pulling strings to commute a sentence for someone, for which 150,000 yuan ($24,407) was charged.

Zhou Bin, son of Zhou Yongkang, was also revealed to have secretly built his business empire through "powerful government connections" by media reports last week. He acquired an affordable housing program in Beijing, and transferred it to a real estate company for profit.

Prior to that, multiple high-ranking officials within the CNPC system and businessmen related to Zhou Bin have been investigated, including Jiang Jiemin, former head of the State-owned Assets Supervision and Administration Commission and former president of CNPC, who was probed in September 2013.

While media reports disclosed the investigations with no specific mention of Zhou Yongkang, he was mentioned for the first time at a high-level political press conference Sunday.

A spokesperson for the session of the National Committee of the Chinese People's Political Consultative Conference said that China will severely punish corrupt officials regardless of the level of their position.

This came in response to a question as to whether Zhou Yongkang, who retired in November 2012, had been investigated.

The speech, along with the recent wave of media reports about people connected to Zhou Yongkang, has led many to wonder whether overseas media reports claiming Zhou Yongkang is being probed are true or not.

Central government launched a campaign last year to crack down on both "tigers" and "flies," specifically referring to officials at all levels who have committed major and minor graft crimes.