At least 17 people were killed while mining illegally at a disused gold mine in Ghana’s central region when the ground caved in on them on Monday, local authorities and eyewitnesses said.

The dead included one of six injured miners who died in the hospital, the Municipal chief executive Peter Owusu-Ashia told Reuters.

“It is an abandoned pit that has attracted a lot of illegal miners,” Owusu-Ashia said, adding that persistent efforts to ward off such activities have proved futile.

He said rescuers had retrieved 16 bodies using excavators and other earth-moving equipment.

It is unclear how many people had gone into the pit at Kyekyewere, but rescue workers believed all those trapped had been recovered.

Illegal mining is a major concern in Ghana’s mining areas where operators use sophisticated tools to process the ore.

At least 15 Chinese illegal miners were repatriated home earlier this month after they were found to have been mining illegally.