Rescue workers in Chile are continuing in their efforts to make contact with 33 trapped miners, the country's Mining Minister Laurence Golborne has said.
Rescuers drilling small shafts to provide oxygen, water and food have made some progress, Mr Golborne, who is overseeing the operation, said.
But it could take up to a week until they reach the miners, he warned.
No contact has been made with the men since a tunnel collapsed on Thursday at the San Jose mine in northern Chile.
The miners were working at a depth of around 450m (1,475ft).
Officials are hoping that the men took refuge in a shelter when the tunnel caved in.
Three teams had been attempting to reach the trapped miners using a ventilation shaft, but this effort was thwarted when a further cave-in blocked the shaft.
Mr Golborne said it could now take at least a week to reach the miners.
"We have gone from hours to days and now possibly a rescue that could take weeks, which is very painful for us and generates a feeling of anger and powerlessness," the minister said.
Dozens of anxious relatives have spent freezing nights and hot days outside the mine waiting for news about the trapped miners.
The San Jose gold and copper mine near Copiapo in the mineral-rich Atacama desert is owned by the private firm San Esteban.
Chilean President Sebastian Pinera said on Sunday that every effort would be made to find the men and that the accident would be thoroughly investigated.
Major mining accidents are uncommon in Chile, the world's top copper producer.