Prosecutors in Shanxi province have approved the arrest of Zhang Xiuping, a former deputy Party chief at Jinzhong, on suspicion of bribery, the Supreme People's Procuratorate announced on Thursday.

The case is still under investigation, according to a statement on the top procuratorate's website that gave no further details.

Four senior officials in Shanxi, including Zhang and another woman, Yang Xiaobo, were expelled from the Communist Party of China and removed from their posts for a "serious violation of discipline and laws", a euphemism for corruption, the province's anti-graft watchdog said on Wednesday. Yang was a former deputy Party chief and mayor of Gaoping, a county-level city.

Zhang and Yang were said to have "committed adultery with others", the first time the anti-graft authorities have used such a term in relation to female officials, the Mirror Evening News reported on Thursday.

The word "adultery" first appeared in a statement about a discipline violation by Dai Chunning, deputy general manager of the China Export and Credit Insurance Corp, released by the top anti-graft authority in June, according to the Beijing newspaper.

CPC regulations say that officials who commit adultery, which is included in a list of breaches of socialist morals, can face penalties ranging from a warning to expulsion from the Party.

So far this year, at least 32 officials have been removed from their positions after being accused by prosecutors of committing adultery, the Mirror Evening News said. Six were provincial-level leaders.

The CPC Central Commission for Discipline Inspection said adultery was not against the law, but was regarded as unacceptable behavior for Party members.

The Beijing News said Zhang was a former colleague of Jin Daoming, who was deputy director of the Shanxi Provincial People's Congress Standing Committee. He was placed under investigation on Feb 27 for what officials described as a "grave violation of discipline and law", and was removed from office on March 1.

Zhang, 49, began to work at the Shanxi Discipline Committee in March 2000, and became a standing member of the committee in October 2006, two months after Jin was appointed the committee secretary. They worked together for seven years before Zhang was transferred to Jinzhong.

Zhang, on Jin's instructions, investigated the case of Bai Peizhong, the former chairman of the State-owned Shanxi Coking Coal Group Co. In November 2011, it was reported that Bai's home had been broken into and 10.78 million yuan ($1.76 million) had been stolen.

Two months after the Jin probe, Zhang came under investigation, a process that continued for seven months and culminated in Wednesday's announcement by the anti-graft authorities.

The shake-up of the leadership in Shanxi began in February. Scores of senior officials were placed under investigation after being accused of "serious violations of discipline and law" by the authorities. A third of the members of the top provincial decision-making body have been investigated since late 2012.