A Tlaxcala state official told CNN affiliate FOROtv at least 11 people died and 70 were injured in the blast, which occurred in east-central Mexico during a religious procession. La Chronica reported Interior Ministry official Luis Felipe Puente said 11 people had died.
State-run news agency Notimex confirmed at least nine worshipers were killed and "an unknown number" were hurt, CNN said.
Mateo Morales Baez told Notimex victims were taken to several area hospitals.
Mexican President Enrique Pena Nieto called it a "terrible accident," La Prensa reported.
"My condolences to the relatives of the deceased," he wrote on Twitter.