Workers collect rocks containing gold at Pongkor gold mine, operated by state miner PT Aneka Tambang Tbk, in West Java

FREETOWN: At least 200 people were killed when a trench collapsed at an unofficial gold mine in Sierra Leone, the West African country’s Ministry of Mineral Resources said on Friday.

The accident occurred in the Bo district in the south of the country, about 180 miles from the capital, Freetown.

“Over 200 gold miners were killed when a …trench dug by the miners collapsed,” a ministry spokesman said.

Unofficial gold mining is common in Africa where miners usually have no professional training or equipment and often dig by hand. Accidents are frequent at the sites, which do not meet safety standards found at professionally engineered mines.

“A forty feet (12 meters) pit was dug out to mine gold,” a senior police source said. “Hundreds of (miners) entered the pit, and when it collapsed it trapped them.”

Children as young as 13 were working in the mine when it caved in, police said, adding that around 20 people escaped.

Officials from the resources ministry were en route to the scene of the disaster on Friday, the ministry spokesman said.

Informal, or artisanal, gold mining is common in mineral-bearing African countries.