The cave-in occurred on the Detroit mine site at around 3pm local time (13:00 GMT) on Friday following heavy rains, said Emiliane Itongwa, president of the Initiative of Support and Social Supervision of Women.
“Several miners were in the shaft, which was covered and no one could get out. We are talking about 50 young people,” Itongwa said.
Photos on social media showed hundreds of people gathered on a hillside around the mine-shaft entrance.
The mine was not located on the Kamituga gold concession owned by Canadian miner Banro Corporation, the company’s chief executive said.
Mining accidents are common in unregulated artisanal mines in Congo, with dozens of deaths every year in mines where often ill-equipped diggers borrow deep underground in search for ore.
A landslide at a disused gold mine killed 16 in October last year, while 43 clandestine miners died in another landslide at a copper and cobalt mine in June 2019.