According to Associated Press reports on Wednesday afternoon, the incident occurred at an operation in northern Coahuila state, about 90 miles (150 kilometers) from the US border city of Eagle Pass, Texas.

Reuters identified the mine as a private operation owned by Federico Quintanilla, citing civil protection representative Juan Antonio Ibarra.

The official also said the explosion may have occurred between 60 and 70 meters (195-228 feet) underground.

“We have no information as to whether they are alive or injured," Ibarra told the news service.

Initial reports indicated seven were trapped underground, but later Wednesday global news services including Reuters updated the count to at least five.

Both reports attributed the numbers to local officials.

Coahuila public safety secretary Jorge Luis Moran told Reuters the blast happened during the early morning hours Wednesday, about 9am local time.

It is not yet known if any other miners were able to escape.

The Mexican state has many small, primitive operations, and methane is considered a common hazard.

In 2006, 65 miners were killed in a similar explosion at the Piedras Negras in Coahuila.

Keep watching ILN for more on this incident.