Mexican President Andres Manuel Lopez Obrador called Sunday for intensified efforts to save 10 workers trapped in a flooded coal mine, during a visit to see firsthand the rescue operation.

Relatives of the missing were becoming increasingly desperate four days after the mine flooded in the northern state of Coahuila, fearing time is running out to bring them out alive.

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.

"We have to do everything we are doing and more" to find the missing miners, Lopez Obrador told reporters during his visit to the site in Agujita.

"I want it to be as soon as possible," he added.

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.

"There is progress. Water levels continue to drop. Much larger volumes continue to be extracted," said Coahuila Governor Miguel Angel Riquelme.

Rescuers were ready to enter the mine "as soon as the levels drop," he added.

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.

Authorities said the miners had been carrying out excavation work when they hit an adjoining area full of water.

The Attorney General's Office said on Sunday that it asked the Ministry of Labor to provide information on safety inspections carried out at mines in the area to determine the cause of the accident.

Lopez Obrador had previously declared Saturday "a decisive day" for the operation.

But by the end of the day, 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."

Some families joined a mass near their improvised camp in the community of Agujita to pray for the safe return of their loved ones.

Water seen flowing from the mine through drainage channels had earlier lifted the hopes of relatives praying that the miners are alive inside a pocket of air.

"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 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.