China’s foreign-policy apparatus is again facing questions about succession after the reported questioning of a top figure who had been widely viewed as the nation’s next foreign minister.

Just two years after the surprise ouster of Foreign Minister Qin Gang, senior diplomat Liu Jianchao has been detained for unclear reasons, according to a Wall Street Journal report. Liu has been heading the Communist Party’s International Department, which conducts outreach to political parties and civic groups around the world and runs in parallel to the Foreign Ministry.

A removal of Liu would create another leadership vacuum in foreign policy just as Chinese President Xi Jinping tries to position China as a more trustworthy partner than the U.S. under President Donald Trump. For now, Wang Yi, who turns 72 in October and has surpassed the once-official retirement age, remains foreign minister and the party’s head of international affairs.