At least nine illegal gold miners have died in Zimbabwe after they detonated explosives underground and were trapped at a mine owned by unlisted London-headquartered Metallon Corporation north of the capital Harare.

Metallon put its Mazowe Mine on care and maintenance last September, citing viability problems. One of Zimbabwe’s biggest gold producers, it still operates three other mines.

Metallon said in a statement the mine collapse happened on Sunday when illegal miners gained access to underground shafts and blasted explosives.

“Tragically nine panners lost their lives. None of these miners were employees of Metallon and all those involved with keeping the mine on care and maintenance have been accounted for,” Metallon said.

At least 24 people died in February when underground shafts were flooded at two abandoned mines in Battlefield, which is to the west of Harare.

Formal unemployment above 80 percent, thousands of young men risk their lives daily working in dangerous underground tunnels in search of gold, Zimbabwe’s largest mineral export earner.

The southern African nation has been working to regulate thousands of people who illegally dig for gold everywhere, including on farms and abandoned mines, mostly under the cover of darkness.