A massive explosion probably caused by a gas leak gutted the ground floor of a building in central Paris's shopping district killing 2 firefighters and a Spanish tourist.

A vehicle is overturned amid debris after the explosion of a bakery on the corner of the streets Saint-Cecile and Rue de Trevise in central Paris on January 12, 2019.
A vehicle is overturned amid debris after the explosion of a bakery on the corner of the streets Saint-Cecile and Rue de Trevise in central Paris on January 12, 2019. (AFP)

A powerful gas explosion tore through a building in central Paris on Saturday, killing two firefighters and a Spanish woman, injuring dozens of people and badly damaging nearby apartments, officials said.

The blast left 47 other people injured, 10 of whom are in a critical condition, the Paris prosecutor's office said.

A source in the Spanish foreign ministry said a woman who was holidaying with her husband in Paris died in hospital after the blast while another Spanish national was also injured.

Around 200 firefighters were mobilised to battle the fire that broke out after the blast and evacuate victims and residents in the area, Interior Minister Christophe Castaner told reporters at the scene.

An investigation was opened to determine the exact cause of the blast, he said.

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.

A helicopter landed in the area to evacuate the wounded. Silver-helmeted firefighters and red firetrucks filled the street and inspected adjoining courtyards. A vehicle from gas company GRDF was stationed nearby.

People are evacuated and treated by emergency workers in a restaurant next to the scene of the explosion of a bakery on the corner of the streets Saint-Cecile and Rue de Trevise in central Paris on January 12, 2019.
People are evacuated and treated by emergency workers in a restaurant next to the scene of the explosion of a bakery on the corner of the streets Saint-Cecile and Rue de Trevise in central Paris on January 12, 2019. (AFP)

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.

Firefighters extinguish a fire after the explosion of a bakery on the corner of the streets Saint-Cecile and Rue de Trevise in central Paris on January 12, 2019.
Firefighters extinguish a fire after the explosion of a bakery on the corner of the streets Saint-Cecile and Rue de Trevise in central Paris on January 12, 2019. (AFP)

Another witness told The Associated Press that she was awakened by the blast, and feared it was another terrorist attack.

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 around the country.

Firefighters run with a stretcher towards the scene of an explosion of a bakery on the corner of the streets Saint-Cecile and Rue de Trevise in central Paris on January 12, 2019.
Firefighters run with a stretcher towards the scene of an explosion of a bakery on the corner of the streets Saint-Cecile and Rue de Trevise in central Paris on January 12, 2019. (AFP)
Source: TRTWorld and agencies