China’s former chief of domestic security, who has been under investigation for months in an anti-corruption inquiry, has been expelled from the Communist Party and arrested, the official state news agency announced early Saturday.

According to New York Times, the former security chief, Zhou Yongkang, is the highest-ranking party leader to be prosecuted since the Gang of Four, including Mao Zedong’s widow, Jiang Qing, were put on trial 34 years ago in the aftermath of the Cultural Revolution.

Xinhua, the official news agency, said in a terse announcement that the decision to expel Mr. Zhou, 72, had been made at a meeting on Friday of the party’s powerful Politburo. It said he also had been placed “under judicial probe,” laying the basis for a prosecution.

Zhou Yongkang amassed so much power while still in office, and his family became enormously wealthy.