China is investigating former President Hu Jintao’s most senior aide, Ling Jihua, state media report.
Ling Jihua is accused of “disciplinary violations”, Xinhua news agency said, which usually refers to corruption.
He was demoted in 2012 after reports that his son had died crashing his Ferrari sports car in Beijing.
Correspondents say the investigation shows current President Xi Jinping feels secure enough to detain even the trusted advisers of his predecessor.
Xi Jinping took over from Hu Jintao as the Communist Party leader and China’s president in late 2012.
Earlier this month it was announced that former Chinese security chief Zhou Yongkang was facing corruption charges – a move that sent shockwaves through the political elite.
A week later, former top economic official Liu Tienan was jailed for life for accepting millions of dollars in bribes.
Critics say President Xi Jinping’s campaign is as much about eliminating political rivals as it is about tackling corruption.
Until the scandal involving his son, Ling Jihua had been tipped for promotion to the party’s Politburo.
Instead, he was moved from head of the Central Committee’s General Office – in effect chief of staff to China’s leader – and appointed to the less influential post of head of the United Front Work Department.
The identity of those inside the Ferrari was never revealed and censors blocked online comments mentioning the crash.
However, reports said Ling Jihua’s son was behind the wheel and the two passengers were described as scantily-clad women.
Ling Jihua was accused of trying to cover up the scandal.
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