Local public security authorities said they had ruled out an “attack” or “event related to a violent act” against civilians.
Sonora Governor Alfonso Durazo said in a video message that “a number of the victims” were minors and that survivors were being treated at hospitals in Hermosillo.
“I have ordered an extensive and transparent investigation to determine the causes of the incident and figure out those responsible,” Durazo said.
“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 said.
Images in local media showed the front of the supermarket charred by the fire, with the windows blown out.
Newspaper El Universal reported that the explosion occurred about 2pm (20:00 GMT) and that nearby businesses closed their doors to prevent the fire from spreading.