Zhou Benshun, the Hebei provincial Communist Party boss who served as a top aide to ex-security tsar Zhou Yongkang, has been placed under investigation for suspected graft, the authorities announced on Friday. Earlier in the day, Zhou Benshun, 62, attended a meeting chaired by Vice-Premier Zhang Gaoli on the integration of Beijing, Hebei and Tianjin . State media initially ran a photo of the two sitting a seat apart, but Zhou was later cropped out. He is the first provincial leader to be detained while still in office in the anti-graft campaign launched by President Xi Jinping. The announcement was made by the Central Commission for Discipline Inspection. When Zhou Yongkang ruled the party's Central Political and Legal Affairs Commission from late 2002 to 2012, Zhou Benshun was his deputy secretary-general and then secretary-general, according to his public profile. He also held key positions in the most powerful divisions of the commission at the time, such as the social stability maintenance office and the Xinjiang affairs coordination office. Roughly four months after Zhou Yongkang retired in late 2012, Zhou Benshun was removed from the public security apparatus and appointed party boss of Hebei. When speculation over whether the former security tsar was being investigated ramped up in late 2013 and his allies began to be detained, many were expecting to see Zhou Benshun fall. But some observers speculated the leadership was giving him another chance when he was included in a group of officials who made self-criticisms in an event broadcast on state television, under the president's watch. The confessions were part of the nationwide "mass line" campaign Xi began to strengthen ties with the people. Xi was in charge of supervising the implementation of the campaign in Hebei. Zhou Benshun was shown on TV criticising himself for making independent decisions, being anxious for quick results, neglecting to thoroughly understand people and failing to work hard enough. At the time observers read his appearance as a sign he might be spared the same fate as his patron. "I've always argued Zhou Benshun would be detained, but it's confusing why Beijing waited until now," said Zhang Lifan , a Beijing-based political commentator. "But before the Beidaihe conference, people are neurotic. Anything could be sensitive and anybody could turn to be an enemy." On Wednesday, Zhou inspected the Beidaihe district in Hebei, weeks before the meeting of party elders and leaders. Zhou Yongkang was sentenced to life in jail on June 11.