Firefighters pulled injured victims from windows and evacuated residents as smoke billowed over Rue de Trevise in the 9th arrondissement of north-central Paris.
The Paris prosecutor’s office said that two firefighters have been killed in the bakery blast, correcting the overall figure of four dead given earlier by France’s interior minister.
Authorities said 10 people were in critical condition and 37 others less seriously injured.
Interior Minister Christophe Castaner told reporters at the scene “unfortunately the human toll is particularly serious.” He paid homage to the courage of rescuers who notably saved the life of one firefighter who was buried under the rubble for two and a half hours.
Paris Mayor Anne Hidalgo, who was also at the scene, extended a “message of affection and solidarity” to the victims.
She said many residents and tourists have been evacuated from neighbouring buildings and hotels. Paris authorities will help provide temporary accommodation, the mayor said.
Paris prosecutor Remy Heitz said that the cause appears to be an accidental gas leak. He said that Paris firefighters were already at the scene to investigate a suspected gas leak at the bakery when the explosion happened.
He told The Associated Press that “the judicial police have started investigating, the scientific police as well. The origin of the explosion seems accidental. We are at the beginning of the investigation everything will be made to establish the exact origin of the explosion as soon as possible.”
Witnesses described the overwhelming sound of the blast and people trapped inside nearby buildings. Charred debris and broken glass covered the pavement around the apartment building housing the bakery, which resembled a blackened carcass.
Authorities said around 200 firefighters and police were involved in the operation.
A helicopter landed in the area to evacuate the wounded. Silver-helmeted firefighters and red fire engines filled the street and inspected adjoining courtyards. A vehicle from gas company GRDF was stationed nearby.
Pedro Goncalves, an employee at the Hotel Mercure opposite the bakery, said he saw firefighters enter the bakery in the morning but he and his co-workers “thought maybe it’s a joke, a false alarm” and they went back to work. About an hour later, he said a blast rocked the surrounding streets.
“In the middle of nothing, I heard one big explosion and then a lot of pressure came at me (and) a lot of black smoke and glass,” he said. “And I had just enough time to get down and cover myself and protect my head.”
Goncalves said he “felt a lot of things fall on me” and that he was struck by shattered glass. He had a few cuts on his head, and spots of blood on his sweater and undershirt.
“Thank god I’m OK,” he said, saying that the blast was so powerful that he heard whistling in his ears in the aftermath. Goncalves said that he ran for the exit and then went to check on the hotel’s clients, adding that some of them had head injuries and were bleeding. He said that the hotel was “destroyed” in the blast.
Another witness told the AP that she was awakened by the blast, and feared it was another terrorist attack.
The bakery is around the corner from the Folies-Bergere theatre 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 around the country.