A fire that broke out at a discount shop in Mexico has killed at least 23 people and injured 11 others, local officials say.

The blaze broke out on Saturday in the centre of the north-western city of Hermosillo at a branch of Waldo's - Mexico's largest discount chain.

Multiple local authorities described the incident as an explosion, though regional Governor Alfonso Durazo said the exact cause had yet to be determined. The Sonora state public security secretariat said it had ruled out the possibility it was an attack or act of deliberate violence against civilians.

Children are among the victims, officials said, with a 15-year-old girl among those taken to the hospital.

Images from the scene show thick, black smoke billowing from the building, with the flames spreading to cars parked in front of the shop.

After the fire was extinguished, scorch marks were visible on the shop's doors and windows, one of which appeared destroyed. The car immediately in front of this window is entirely burnt out.

"To the families who lost a loved one... I share your pain and offer you my full solidarity," Durazo said in a video address.

He added that an "extraordinary, transparent and thorough" investigation had been launched to clarify the causes of the incident and determine who was responsible.

Sonora state's Attorney General Gustavo Salas Chávez told reporters early on Sunday that most of those killed had died due to "exposure to toxic gases".

He said there was no indication that the fire had been started intentionally, but added that he could not rule out an investigation into the cause.

Mexican President Claudia Sheinbaum wrote on social media: "My heartfelt condolences to the families and loved ones of those who lost their lives."

Waldo's shops are a common sight on Mexican high streets, with hundreds of outlets across the country.

The fire comes on the weekend when Mexico celebrates the Day of the Dead, where festivities are held for people to honour deceased loved ones.

The state government said it was cancelling cultural events planned for Sunday after the incident.