Efforts to rescue 65 miners trapped in a mine in Mexico encountered new obstacles on the fifth day, as hopes dimmed for finding any of them alive.
Rescue teams Thursday passed a checkpoint where they expected to find at least two of the workers trapped since the explosion on Sunday.
But there was no sign of the two and air quality and digging conditions continued to worsen as teams dug deeper into the Pasta de Conchos mine in northern Mexico.
Officials expect levels of harmful methane gas to be higher in deeper parts of the mine.
The 65 trapped workers were carrying only a few hours' worth of oxygen with them at the time of the blast.
Rescuers are using hand tools to advance through the damaged tunnels, fearing power machinery could trigger another blast.
Family and friends are keeping a grim vigil outside, braving bitterly cold temperatures at night as they wait for news.Some information for this report was provided by AP and Reuters.