The 28-year-old forward was contracted to the Chinese Super League side after joining them this year, but he sadly passed away at his residence, according to a report by CBS News.
In a statement posted to social media on Wednesday, the Gabonese Football Federation extended heartfelt condolences to Boupendza's family and praised the late player for his contributions to the national team, especially during the 2022 Africa Cup of Nations (AFCON), where he scored the decisive goal in their victory over Comoros.
"The club is now fully cooperating with the relevant departments to carry out the investigation," the federation said.
"The Gabonese Football Federation and the wider Gabonese football family offer their sincere condolences to his biological family during this difficult time."
French side Bordeaux, where Boupendza began his professional career, also paid tribute on X, describing his death as "tragic" and sending their thoughts to his family and the football community.
Boupendza's career began in France with stints at Bordeaux's reserve team, Pau FC, Gazelec Ajaccio, and Tours. His breakthrough came during the 2020-21 season with Hatayspor in the Turkish Super Liga, where he netted an impressive 22 goals.
Hatayspor also posted a message of mourning on social media: "Rest in peace King."