An official statement gave no more details but the wording suggested Zheng had killed himself.
China's top representative in Macau has fallen to his death from the building where he lived, authorities said Sunday.
Zheng Xiaosong, 59, the Chinese government's liaison officer in the semi-autonomous former Portuguese colony, had been suffering from depression, Beijing said in a statement.
Zheng "fell to his death from his Macau residence on the evening of October 20, 2018 due to depression", the Hong Kong and Macau Affairs Office of the State Council said.
The statement gave no more details but the wording suggested Zheng had killed himself.
Mainland officials were to travel to Macau on Sunday to express their "condolences to comrade Zheng Xiaosong's family" on behalf of the Chinese government, it added.
The director of Macau's judiciary police said they were investigating Zheng's death, Hong Kong media reported.
Zheng, a member of the ruling Communist Party's Central Committee, was reportedly involved in talks between London and Beijing ahead of the handover of Hong Kong in 1997.
He took up the post in the gambling enclave of Macau last year. The territory operates under the same "One Country, Two Systems" principle that governs Hong Kong.
Hong Kong leader Carrie Lam said in a statement that she was "grieved to learn of his sudden departure".
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