The incident happened on Tuesday in the Sabon Gari area of the city, mostly populated by people who moved to Kano from elsewhere.
Mustapha Habib Ahmed, head of the National Emergency Management Agency, said a gas cylinder in a welding shop exploded, killing nine people. Emergency responders pulled bodies from the rubble during a search and rescue operation.
At a nearby school, parents rushed to pick up their children after hearing news of the blast, witnesses said. There were no reported injuries among the school children.
Kano, renowned for centuries as a centre for Islamic scholarship and a commercial hotspot in trans-Saharan trade, is the capital of the eponymous Nigerian state in the northwest region of the country.