A gas buildup in a northern Mexico coal mine triggered a pre-dawn explosion Sunday, trapping at least 65 coal miners underground with a limited supply of oxygen. Emergency officials were tunneling through the debris to rescue them.

At least eight miners who had been near the mine's exit when the explosion occurred were rescued and were hospitalized with burns and broken bones.

Union and company officials said they believed there were 65 miners trapped in various places throughout the mine, near the town of Sabinas, 85 miles southwest of Eagle Pass, Texas. Rescue officials had not been able to make contact with the trapped miners.

Juan Rebolledo, vice president of international affairs for mining giant Grupo Mexico, which owns the mine, said several rescue teams were taking turns carefully removing debris that had clogged the steep shaft.

"It's slow work because of the quantity of debris," he said.

Rebolledo said officials were unaware of the miners' conditions. He said oxygen tanks were scattered throughout the mine, but it was impossible to know if the trapped miners had access to them or how long they could survive before rescue workers reached them. The explosion occurred around 2:30 a.m. Sunday local time.

Coahuila Gov. Humberto Moreira Valdes, who was at the site overseeing the rescue operation, told Televisa network that the mine's ventilation system was still working. The mine was about 985 feet below the ground.

Officials had cordoned off the area, and family members waited outside the security zone for information.

Daniel Romo, a spokesman for Coahuila state's emergency services, said authorities did not know how long it would take to reach the trapped miners.

Consuelo Aguilar, a spokeswoman for the National Miners' Union, said union officials were also at the scene.

She said there has been concern over safety conditions in Grupo Mexico mines.

"We have pressured for better safety conditions as well as for better pay at the mines," she said.

She called for an investigation to determine the cause of the accident and the responsibility of any company officials.

Rebolledo said safety conditions at the mine met Mexican government requirements as well as international standards.

"We follow all the best safety procedures, but accidents can always happen," Rebolledo said.

The company discusses safety conditions with the union in annual meetings and there has been no major disagreement on the issue, he said.

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

There have been various fatal mining accidents in Coahuila. The worst was in 1969 when more than 153 miners were killed in a pit at the village of Barroteran. In 2001, another 12 people died in an accident at a mine near Barroteran.

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

(Source: AP)