At least 78 people have died after authorities imposed a blockade on an illegal gold mine here, part of a monthslong standoff between prospectors and a government determined to force them to surface—often by cutting off their food and water.

The South African government has launched a rescue operation at an abandoned gold mine in the country’s North West province, where at least 109 men have died, a group representing the miners said, after local authorities cut off vital supplies in a dramatic bid to crack down on the country’s illegal mining trade.

Arguing that the miners had entered the mine without permission, authorities reportedly cracked down by cutting off their access to food and water.