According to local media as well as Reuters, the blast occurred Friday morning at an Altos Hornos de Mexico operation in the Coahuila state.

The company said a pocket of methane ignited at the mine, resulting in the collapse of about 110 tons (100 tonnes) of coal and the evacuation of nearly 300 workers.

As of Saturday morning local time, the bodies of six miners had been recovered and one individual was rescued.

Another five remain trapped underground, half of the initial entrapment of 10 miners just after the incident.

“We are devoted to the rescue of the affected miners,” Coahuila public safety secretary Jorge Luis Moran told Reuters.

Moran added that AHMSA had a reputation for safe operations.

Friday’s explosion is the second in 10 days in Mexico. Both have occurred in the Coahuila state.

On July 25, seven miners were killed at a private operation owned by Federico Quintanilla.

Officials have cited subpar safety conditions at Mexico’s small mines, which often are poorly regulated, for that accident.

A 2006 explosion at Grupo Mexico’s large Piedras Negras mine, also stemming from a methane accumulation, killed 65 miners.