Mexican army divers have been blocked by debris in their first attempt to descend deep into a flooded coal mine in northern Coahuila state, where 10 miners have been trapped for a week.
"It [mine] has been blocked," Defence Minister Luis Cresencio told the media on Thursday.
"There is no space to move forward, there are obstructions ... there are still some planks of wood. Even with their lights to see inside, they don't have the necessary visibility to identify what they're finding," Cresencio said.
Cresencio added that officials will continue efforts to enter the mine while ensuring the safety of rescue teams.
The water depths in the three shafts measure about 30 feet, 23 feet and 16 feet.
Unsafe conditions for mission
Two military divers entered one of the three flooded mine shafts on Wednesday after a miner and a rescue professional submerged four times to clear debris but were unable to fully enter the mine.
Mexican rescuers managed to dramatically reduce water depths that initially had topped about 100 feet, but have struggled to send in rescue teams even on preliminary efforts to gauge whether conditions would be safe for a rescue mission.
The miners became trapped on August 3 when their excavation work caused a tunnel wall to collapse, triggering flooding in parts of the underground mine.