Ren Runhou, former vice governor of the northern province of Shanxi, "passed away of illness while under investigation" the party's disciplinary agency said on its website.
The inquiry into Ren began last August and respected news outlet Caixin reported he died a month later from cancer, aged 57.
The party announced that Ren had been "stripped of his party membership", on the grounds that he had embezzled public funds and accepted bribes to seek promotions for others.
Property amassed by Ren from his suspected embezzlement and bribery will be transferred to judicial officials, according to the CCDI.
Since coming to power in 2012 China's President Xi Jinping has vowed a crackdown on endemic graft by Communist party cadres.
The ruling party's internal investigations operate without any legal oversight, and since 2007 more than 15 officials have reportedly died from abuse while under such probes.