Chinese authorities have seized assets worth at least $14.5 billion from family members and associates of retired domestic security chief Zhou Yongkang, who is at the center of China’s biggest corruption scandal in more than six decades, two sources said.

More than 300 of Zhou’s relatives, political allies, proteges and staff members have been detained or questioned in the past four months, said sources who were briefed on the investigation.

The sheer size of the asset seizures and the scale of the investigation make the corruption probe unprecedented in modern Chinese history and would appear to show that President Xi Jinping is tackling graft at the highest levels.

But it may partly be political payback. Zhou angered Xi and other leaders by opposing the ouster of former high-flying politician Bo Xilai, who in September was sentenced to life in prison for corruption and abuse of power.

Zhou, 71, has been under virtual house arrest since authorities began formally investigating him late last year. He is the most senior Chinese politician to be ensnared in a corruption investigation since the Communist Party came to power in 1949.

“It’s the ugliest in the history of the new China,” said one of the sources, who has ties to the leadership and spoke on the condition of anonymity to avoid repercussions for talking to a foreign news organization about a sensitive subject.

The government has yet to make an official statement about Zhou or the case against him, and it has not been possible to contact Zhou, his family, associates or staff members for comment. It is unclear whether any of them have hired attorneys.

The party’s anti-corruption watchdog and the prosecutor’s office did not respond to requests for comment.

Xi ordered a task force formed in late November or early December to look into accusations against Zhou, sources have previously told Reuters. The sources have not said what the allegations were except that they were related to violating party discipline — official jargon for corruption.

A third source with ties to the leadership said Zhou had refused to cooperate with investigators, insisting he was the victim of a power struggle.

“Zhou Yongkang is tough and claims it’s political persecution,” the source said.

— Reuters