Informal gold miners in eastern Democratic Republic of Congo scoured rubble on Saturday for more than 50 colleagues presumed dead after an artisanal gold mine collapsed near Kamituga in the east of the country under the weight of heavy rain.

Hundreds of young men in rubber boots crowded around the site of Friday’s cave-in, with some removing rocks by hand from the muddy hillside, video footage showed.

Dozens of people die each year in accidents in largely unregulated artisanal mines in Congo, where often ill-equipped diggers borrow deep underground in search for ore.

Alexandre Bundya, mayor of the nearby town of Kamituga, Mpila, ordered two days of mourning. The office of the governor of South Kivu province, Theo Kasi, said most of the victims were young people and expressed condolences to their families.

“The search continues to identify our deceased compatriots, bring assistance and implement measures to prevent such incidents from repeating,” Kasi’s office said in a statement.

A World Bank report last year estimated the number of small-scale miners in Congo at 2 million, many more than work in industrial gold, copper and cobalt mines owned by companies like Glencore and Barrick Gold.