Mexican President Andres Manuel Lopez Obrador said that he would visit a disaster-hit coal mining region on Sunday to see firsthand a major operation to try to rescue 10 workers.
Relatives of those trapped were becoming increasingly desperate four days after the mine flooded in the northern state of Coahuila, fearing time is running out to save them.
Nearly 400 soldiers and other personnel, including six military scuba divers, have joined the rescue effort but so far it has been too dangerous to enter the mine, authorities said.
"I'm going to see how the rescue's going. I'm going to the situation," Lopez Obrador told reporters during a trip to the western state of Colima.
He had earlier declared Saturday "a decisive day" for the operation in Agujita, which is in the municipality of Sabinas.
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"According to the experts, we'll know if it's possible for the divers to enter safely," he tweeted.
The focus has been on pumping out water from the mine to make it safe enough to descend into the shafts, which are 60 meters (200 feet) deep.
Five workers managed to escape from the crudely constructed mine in the initial aftermath of the disaster, but since then, no survivors have been found.
Coahuila's state government said the miners had been carrying out excavation work when they hit an adjoining area full of water.
By late Saturday the water inside the mine had receded only about 9.5 meters from the initial 34 meters, authorities told relatives.
Liliana Torres, the niece of one of the missing workers, said that she had witnessed the relentlessness of rescuers who "do not stop all day," but added that the families were increasingly "desperate."
After Saturday ended without success, some families joined a mass near their improvised camp in the community of Agujita.
Water seen flowing from the mine through drainage channels had earlier lifted the hopes of relatives anxiously awaiting news.
"We're still hoping that they're in a higher part (of the mine), although there's too much water... but we trust in God," Elva Hernandez, mother-in-law of one of the trapped workers, told AFP.
The Coahuila State prosecutor's office said it had interviewed the five workers who managed to escape from the crudely constructed mine.
"Apparently they were expelled by a torrent of water," Coahuila attorney general Gerardo Marquez told the press.
He added that his office had requested information from the landowner and mine concession holder, but declined to name them.
Experts detected a leak coming from nearby mines and were trying to find its exact location so they can stop water from flowing into the area where the workers are trapped, Coahuila's labor secretary, Nazira Zogbi, said on Saturday.
A French company has provided equipment to assist in the task, she said, without naming the firm.
Coahuila, Mexico's main coal-producing region, has seen a series of fatal mining accidents over the years.
Last year, seven miners died when they were trapped in the region.
The worst accident was an explosion that claimed 65 lives at the Pasta de Conchos mine in 2006.
Only two bodies were retrieved after that tragedy.