Hopes of finding the 65 Mexican workers trapped underground in a coal mine are almost gone, but rescuers have not altogether ruled out finding survivors.
Anxious relatives continue to wait for news of loved ones
The men have been stuck deep in the mine in the northern state of Coahuila since an explosion three days ago.
It is thought their limited supplies of oxygen would have run out by now.
However, Mexican officials say some miners might have survived if ventilators in the shaft worked and air pockets developed.
Rescuers believe they are hours away from reaching the first group of trapped workers, but efforts have been hampered after a section of the shaft collapsed.
On Wednesday, Ruben Escudero, a spokesman for the company that owns the mine, said some progress had been made with part of the damaged structure being repaired to allow more oxygen to circulate through the tunnels.
Family members have camped out through the cold desert nights of northern Mexico, complaining about the lack of news.
Some have lit candles praying for a miracle, but others are giving up hope.
A number of relatives panicked when the local newspaper ran a banner headline about the miners which read: "They are surely dead".
The Mexican authorities said they still have not made contact with the miners.
Coahuila state Civil Protection Director, Arturo Vilchis, insisted: "Officials can't speculate on the condition of the miners."
Using picks, shovels and their hands, rescue crews have been working around the clock to get closer to the trapped men.
With methane gas still in the mine, the searchers are not using mechanical equipment for fear of new explosions, and they are making slow progress.
The US Mine Safety and Health Administration is sending a team of experts to the operation at the mine, which lies near the town of San Juan de Sabinas, 100km (60 miles) from the Texas border.
Late on Tuesday, rescuers said they were within 50m of where some miners were working when the explosion occurred at 0230 local time (0830 GMT) on Sunday.
But most of the workers are thought to be trapped in tunnels at least 2km (1.25 miles) into the mine.
Ten men who were underground escaped safely, and another 12 were rescued, suffering from burns and broken bones.
The explosion is thought to have been caused by gases igniting.
A growing number of miners said they had complained in previous weeks about the smell of gas, but were told to keep working.
The owners of the mine, Grupo Mexico, have denied workers' claims that safety procedures were not followed.
The mine passed a labour ministry safety check only two weeks ago, a mine official said.
Mexico's National Miners Union has called for a full investigation as soon as the rescue operation is completed.
There have been a number of fatal mining accidents in Coahuila state. The worst was in 1969, when more than 153 miners were killed in a pit at the village of Barroteran.
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