Zimbabwe’s miners’ federation on Thursday said that at least 40 informal miners were trapped after a shaft in a disused gold mine collapsed, reported AFP.

According to Wellington Takavarasha, head of the Zimbabwe Miners Federation, the incident occurred late Wednesday in the town of Bindura, around 70 kilometres (43 miles) north of the capital Harare.

He told AFP that the miners were working inside the disused Ran Gold Mine when a shaft caved in. Six of the miners since the collapse have been pulled from the rubble and taken to hospital.

Takavarasha said, “Those who were rescued said there were about 40 people in the mine shaft at the time of the incident.”

Gold alone accounts for 60% of exports in Zimbabwe, where mining is a major source of foreign currency. The African nation  is home to vast gold and mineral reserves, including diamonds and platinum.

According to the International Crisis Group (ICG), the gold sector provides jobs to nearly 10% of the country’s population.

Small-scale miners often operate illegally to avoid selling their bullion to the state-owned buyer, Fidelity Printers and Refiners, as they are paid only 55% in foreign currency.

The remaining 45% is paid in Zimbabwean dollars, which is notorious for its weakness.

Accidents are relatively common in decommissioned mines, particularly when the ground is loosened by rain.