Interior minister Christophe Castaner said "the situation is under control" but warned the explosion had caused a "heavy toll." Speaking from the spot of the incident, he said, some 200 firefighters were involved in the operation.
An investigation was opened, according to the Paris prosecutor's office, which would not comment on what possible causes were being investigated.
Silver-helmeted firefighters and red firetrucks filled the street and inspected adjoining courtyards. A vehicle from gas company GRDF was stationed nearby.
The bakery is around the corner from the Folies-Bergere theater and not far from the shopping district that includes the famed headquarters of Galeries Lafayette.
The explosion came as the French capital is on edge and under heavy security for yellow vest protests expected later on Saturday around the country.