Rescue workers searching for 65 coal miners trapped deep beneath the desert scrub of northern Mexico made excruciatingly slow progress Tuesday, working with picks and shovels as anguished relatives demanded information.

More than two days after a gas explosion filled tunnels with fallen rock, wood and metal, rescuers have found no sign of the workers — either dead or alive — in the Pasta de Conchos mine, about 85 miles southwest of Eagle Pass, Texas.

Crews wearing gas masks and oxygen tanks got through one wall of debris, only to encounter another about 1,800 feet inside the tunnel early Tuesday. At least two conveyer belt operators may be just beyond the wall, but most of the other miners were thought to be as far as one to three miles from the mine's entrance.

A power outage briefly struck the ventilation system that officials were counting on to pump fresh air to any survivors, but a backup diesel generator quickly kicked in and kept the fans going until power was restored, said Javier de la Fuente, an engineering contractor with the mine's owner, Grupo Mexico.

Each miner carried tanks with six hours of oxygen at the time of the blast and it was impossible to know if anybody was receiving air through ventilation shafts and oxygen tanks that were scattered throughout the mine, officials said.

Because of fears that electric or gas-powered machinery could spark more explosions, rescuers have had to use picks and shovels to move tons of fallen dirt, rock, wood and metal.

The miners' relatives begged for any information — no matter how bad.

"Just tell us and get it over with," said Maria Trinidad Cantu, who has camped out at the site awaiting word of her 32-year-old son Raul Villasana. "Why don't you tell us the truth? If it was something awful, OK, but we are strong enough to take it."

Some panicked upon seeing a banner headline in Tuesday's local newspaper, La Prensa de Monclova, that quoted a surviving miner as saying: "They are surely dead."

"Did you see what the newspaper said?" asked Salvador Estrada, whose son-in-law is trapped in the mine, speaking to state Civil Protection Director Arturo Vilchis. "The newspaper is saying everyone is dead. Who gave that information? Why are they saying that?"

Vilchis said officials "can't speculate on the condition of the miners."

Neither could de la Fuente, who has 48 years of experience in mining.

Asked if the miners might be alive, he replied: "Can you tell me what lottery number is going to win tonight?"

The trapped miners may not be together. They were installing wooden and metal supports in the top three of four recently dug extensions of the mine when the gas exploded at about 2:30 a.m. Sunday, filling the tunnels with toxic fumes.

At least a dozen other workers near the entrance were able to escape with broken bones and burns.

U.S. mining experts were expected to join the increasingly desperate search, said Juan Rebolledo, vice president of international affairs for mine owner Grupo Mexico SA de CV., but he wasn't sure when they would arrive.

Consuelo Aguilar of the National Miners' Union called for an investigation into Grupo Mexico's responsibility for the disaster.

Rebolledo said safety conditions met national and international standards, "but accidents can always happen."

And Pedro Camarillo, a federal labor official, said nothing unusual was found during a routine evaluation Feb. 7.

As well as mining coal, Grupo Mexico SA de CV is the world's third-largest copper producer, with operations in Mexico, Peru, and the United States.

The Mexican state of Coahuila has been the site of other fatal mining accidents — the worst in 1969 when more than 153 miners were killed in a pit at the village of Barroteran. In 2001, 12 people died in an accident at a mine near Barroteran.

Last month, 14 miners died in two accidents at mines in West Virginia. Two men died in a fire Jan. 21 at a mine in Melville, nearly three weeks after 12 men died after an explosion at the Sago mine near Tallmansville.

In Canada last month, 72 potash miners walked away from an underground fire and toxic smoke after being locked down overnight in airtight chambers packed with enough oxygen, food and water for several days.