Witnesses say Wang Yi, the Chinese government’s top diplomat, walked out before the start of a gala dinner of foreign ministers at a conference in Cambodia on Thursday and was spotted leaving the site in a car.

According to Reuters journalists, Wang Yi waved to the reporters as he entered a holding room for the meal, then walked out without explaining why. Wang Yi was spotted departing in a car, according to two witnesses working at the event.

More than a dozen foreign ministers attended the event, including US Secretary of State Antony Blinken, Japan’s Yoshimasa Hayashi, and top diplomats from the Association of Southeast Asian Nations (ASEAN).