Communist Party authorities are investigating Ling Zhengce, a brother of Ling Jihua - the key aide to former president Hu Jintao accused of covering up a Ferrari crash that killed his son.
The move underscores the widening crackdown against corrupt officials in coal-rich Shanxi province and suggests investigators could be closing in on Ling Jihua himself.
The party's top anti-graft agency yesterday announced the investigation into Ling Zhengce, a vice-chairman of Shanxi province's political advisory body, and a separate inquiry into Vice-Governor Du Shanxue. Both were suspected of serious violation of law and party rules.
Ling Zhengce, 62, is one of the three elder brothers of Ling Jihua. His phone was switched off yesterday.
Ling Jihua, once a promising rising star, suffered a serious setback to his career after his suspected involvement in covering up the March 2012 Ferrari crash in Beijing that killed his son and seriously injured two women passengers. He failed to win promotion to the Politburo later that year.
Ling was transferred to lead the party's United Front Work Department and was later made vice-chairman of the country's top political advisory body, which some analysts viewed as a political soft landing.
But speculation persisted that Ling might eventually fall under the scrutiny of the administration of President Xi Jinping.
Zhang Ming, a professor of political science at Renmin University in Beijing, said Ling Zhengce's detention could be the prelude to an investigation into his younger brother.
"The final outcome … remains unknown but so far Ling Jihua has been clearly targeted," Zhang said. "No one can survive the party's scrutiny."
A Shanxi native, Ling Jihua was said to be a founder of the so-called "Shanxi gang", including officials who worked their way up the ranks in the province.
Dozens of Shanxi officials have been detained this year, including Shen Weichen, the former head of the China Association for Science and Technology who was once party chief in Shanxi's capital, Taiyuan.