MEXICO CITY, Mexico (AFP) — A supermarket explosion killed at least 23 people in northern Mexico on Saturday, according to local officials, with investigators saying the blast was an accident possibly caused by a faulty electric transformer.

"Sadly a number of the victims we've found were minors," Alfonso Durazo, governor of Sonora state, said in a video message as he announced the toll of 23 dead and another 11 injured.

Durazo said the survivors were being treated at hospitals in the city of Hermosillo, where the explosion took place.

"I have ordered an extensive and transparent investigation to determine the causes of the incident and figure out those responsible," he said.

The prosecutor's office said in a statement that "the working assumption is that the incident was accidental, and the investigation is looking into a transformer located inside the store."

"Once the firefighters allow access into the building... it will be possible to precisely determine the cause of the incident," it added.

The explosion happened at a Waldo's store in the city center.

"Nobody will face this pain alone. From the very first moments, emergency, security and health services responded with great professionalism and commitment, controlling the situation and saving lives," the governor said.

Mexican President Claudia Sheinbaum expressed her condolences on X "to the families and loved ones of those who died."

"I have been in contact with the Sonora governor, Alfonso Durazo, to provide support where needed. I've instructed Interior Secretary Rosa Icela Rodriguez to send a support team in order to assist the families and the injured," she continued.

Mexican media reports said customers sought refuge inside the store after the explosion, only to become trapped by the flames.