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About 80 miners were inside the Pasta de Conchos mine, owned by Industrial Minera Mexico, located in a town in the remote, semi-desert state of Coahuila, when the explosion occurred.
Local authorities said 15 miners were rescued from the pit, and eight of them have had surgery to treat injuries, mostly burns.
Rescuers, including soldiers and civil protection staff, have used equipment to try to reach the trapped miners, but have not yet been able to make contact, according to a mine manager.
"The information that we have is that 66 people are trapped and seven others, who were outside the mine but affected by the explosion, are injured," said Miguel Angel Beltran of the civil protection agency in the state capital Saltillo.
The explosion occurred at 2am local time on Sunday, apparently caused by gases that ignited, and caused earth to crumble in a section of the pit, trapping the workers.
Due to the mine's depth it is not known whether the trapped miners are dead or alive.
"Right now we are working on getting out the gas," said Coahuila Red Cross spokesman Sergio Guajardo.
"The ventilators are working at full speed."
Many relatives of trapped miners have rushed to the scene of the accident, a public security spokesman told AFP on the phone.
"There's a lot of people, anxious women, crying and asking about their husbands and brothers," he said.
About 95 percent of Mexico's coal reserves are in Coahuila state, which borders the US state of Texas.
More than 150 coal miners died when an explosion collapsed tunnels more than 30 years ago in the state.
Another local mine explosion killed 37 people in 1998.