Nuevo Leon state public safety chief Jorge Camacho Rincon said the charred remains of five people were found in a field just outside the city.
Authorities said that two drills were found near the scene of the blast. They believe that the accident may have been caused by people trying to install their own illegal hookup.
Theft of utilities such as gas and water is not rare in Mexico.
Lately, drug cartels have become involved, apparently as they seek to diversify their sources of revenue, authorities said.