(CNN) At least 91 people were killed in central Mexico after a ruptured gasoline pipeline exploded Friday evening, Omar Fayad, governor of the State of Hidalgo, said Tuesday.

The death toll has risen since Sunday, when officials said the explosion had killed 79 people and injured 66.

Fayad said some of the injured are minors who will receive treatment at Shriners Hospital for Children in Galveston, Texas.

Photos: In photos: Mexico gasoline pipeline explosion A fire rages after a gasoline pipeline explosion Friday, January 18, in Tlahuelilpan, Mexico, about 80 miles north of Mexico City. Hide Caption 1 of 8 Photos: In photos: Mexico gasoline pipeline explosion Relatives cry after recognizing the body of a loved one in the deadly pipeline blast on Saturday, January 19. Hide Caption 2 of 8 Photos: In photos: Mexico gasoline pipeline explosion Firefighters stand at the scene of the explosion January 18 in Tlahuelilpan. Hide Caption 3 of 8 Photos: In photos: Mexico gasoline pipeline explosion Villagers implore members of the military to let them look for missing relatives January 19. Hide Caption 4 of 8 Photos: In photos: Mexico gasoline pipeline explosion Firefighters work to control the fire January 19. State oil company Pemex initially blamed illegal taps in the pipeline for the explosion. It later said it was launching an investigation into the cause of the blast. Hide Caption 5 of 8 Photos: In photos: Mexico gasoline pipeline explosion An aerial view shows the scope of the disaster scene January 19 in Mexico's Hidalgo state. Hide Caption 6 of 8 Photos: In photos: Mexico gasoline pipeline explosion Forensic doctors work at the scene of the pipeline explosion January 19. Hide Caption 7 of 8 Photos: In photos: Mexico gasoline pipeline explosion Doctors place bodies in vans January 19 in Tlahuelilpan. Hide Caption 8 of 8

Alejandro Gertz Manero, general prosecutor of Mexico, said Saturday night that the investigation has just started but that a "preliminary belief" is that static electricity from the clothing of people around the pipeline may have caused the blast.

He noted a large number of people were around the pipeline, some of whom were wearing clothes made with synthetic fibers that could "generate electric reactions."

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