Falling rocks injured a worker trying to secure an unstable ceiling in the Underground Warehouses, the Tri-Township Fire Department said.
The accident happened shortly after 9 a.m. Sunday within the caves located off Gardner Expressway outside of Quincy.
The man was an employee of Precision Mine Repair, of Ridgway, Illinois contracted to repair the cave ceiling, Tri-Township Fire Department Lt. Chris Costigan said.
Rocks fell as the worker tried to insert bolts into the shelf rock to secure the area that had potential to fall, Costigan said.
The rocks struck the man who was standing in a scissor lift.
The man was able to free himself from the debris before emergency workers got to the scene.
"We were advised that he was able to get out on his own and had some minor injuries," Costigan said.
The man was taken to Blessing Hospital for treatment of his injuries.
The area was cordoned off temporarily until inspectors could visit the cave and determine whether work could continue, Costigan said.
Officials with Underground Warehouses have not returned phone calls seeking comment.
Precision Mine Repair officials also declined to comment.