The Communist Party of China's discipline inspection team in Hunan province has announced it is investigating 431 CPC members and government workers on suspicion of electoral fraud in December 2012 and January 2013.
Those suspected of having broken the law will be passed on to judicial authorities, the inspection team said.
The news follows a statement from the provincial legislature on Saturday that more than 500 local lawmakers had been disqualified, dismissed or have resigned over the electoral fraud in Hengyang, the second-largest city in Hunan.
Altogether 527 city lawmakers were present at the election of provincial lawmakers during the first session of the 14th Hengyang people's congress between Dec 28, 2012, and Jan 3, 2013.
Preliminary investigations have shown that the 56 lawmakers elected offered 110 million yuan ($18 million) in bribes to 518 city lawmakers and another 68 staff.
The provincial legislature disqualified the 56 during a plenary meeting that concluded on Saturday, and legislative bodies in Hengyang accepted the resignations of 512 people who took the bribes.
Another five provincial lawmakers who were not found to have offered bribes were nonetheless dismissed for "serious dereliction of duty", according to the statement from the provincial legislature. Three municipal lawmakers who did not accept bribes resigned, also for "serious dereliction of duty".
Another six who took bribes had already been transferred outside of the city and were no longer in their posts.
Tong Mingqian, then Party chief of Hengyang and in charge of the election, was sacked from his new post as vice chairman of the Hunan Provincial Committee of the Chinese People's Political Consultative Conference on Dec 21.
The statement from the legislature said the fraud, which involved a huge number of lawmakers and a large amount of money, is extremely serious and has had a very negative impact.
"This is a challenge to China's system of people's congresses, socialist democracy, law and Party discipline," it said