Eighteen miners were left trapped underground after an earthquake struck a copper mine in south-west Poland, the operator said early Wednesday.
It was not clear whether the miners were hit or injured by the cave-in late Tuesday or simply cut off, Dariusz Wolski, spokesman for mining company KGHM, told Polish news broadcaster TVN 24.
"We have no contact with them. All telephone and other connections have been interrupted."
The 4.7-magnitude earthquake hit late Tuesday, burying another four miners at the mine who were able to make their way out. A total of 42 miners were working in the affected area at the time.
The missing miners were each carrying emergency breathing equipment with air for eight to nine hours, Wolski said.
Rescue workers abandoned a first attempt to dig through to the miners after several rockslides, but had started digging from a different place in the tunnel system, he said.