Seven miners trapped in a coal mine were killed by an explosion early Wednesday in the town of Muzquiz, in Mexico' s northern state of Coahuila, local police authorities said.

The blast at 8:30 am local time (1330 GMT) appeared to have been caused by a pocket of accumulated gas inside the 73-meter-deep mine.

Coahuila' s Public Security Secretary Jorge Luis Moran confirmed officials had recovered the bodies of the seven miners, who ranged in age from 20 to 39, and taken them to the local forensics center for autopsies.

The latest blast served to again highlight the hazardous conditions at many mines throughout northern Mexico, especially Coahuila.

Media sources said inspectors had in the past fined the operators of the coal mine, the El Progreso mining company, for failing to meet safety standards.

Minutes before news of the explosion, Coahuila state Governor Ruben Moreira told reporters at an official event that he wanted the state and federal governments to work together to increase safety at the mines.

One of the worst mining accidents in recent years occurred in February 2006 at Coahuila's Pasta de Conchos mine, where 65 miners were killed by a methane explosion.