Twelve people have been rescued from an informal gold mine in eastern Congo that collapsed over the weekend, trapping an unknown number of the thousands of miners working there, the provincial governor said Wednesday.

The Lomera gold mine in the South Kivu province collapsed on Sunday following a landslide, burying numerous miners working in the underground tunnels, Gov. Patrick Busu bwa Ngwi Nshombothe said in a statement following his visit to the site.

Nshombothe, who was appointed by a rebel group that controls the area, said over 4,700 miners work on the site and the death toll and number of miners missing are unknown. Search and rescue efforts continue.