Eight underground workers are missing at Trevali Mining's Perkoa mine in Burkina Faso following heavy rains and flooding, the company said.
Operations at the zinc mine have been suspended.
"We are deeply saddened by this unexpected event," chief executive Ricus Grimbeek said.
"Our immediate focus is on search and rescue. We will provide further updates as the situation unfolds and we determine the cause of the flooding event. Our thoughts are with the family, friends, and colleagues that have been impacted."
Trevali Mining owns 90% of the Perkoa mine, located to 120 kilometers west of Burkinabe capital Ouagadougou.
The mine complex includes a 2,000-tonne-per-day processing mill, a flotation recovery plant, and a tailings treatment facility. It also has metallurgical and geochemical laboratories on-site.
The mine contains measured resources of 1.51 million tonnes at 12.72% zinc for 424 million pounds of zinc, and indicated resources of 1.20 million tonnes at 9.48% zinc for 675 million pounds of zinc.
Trevali's guidance for 2022 zinc production is estimated to be between 274 and 280 million pounds of payable zinc, 36 to 41 million pounds of payable lead, and 688 to 778 thousand ounces of payable silver.
Trevali operates the Percoa mine, the Caribou zinc-lead-silver mine in New Brunswick, Canada, and the Rosh Pinah zinc-lead-silver Rosh Pinah mine in Namibia.