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PARIS — Two firefighters died when a large explosion tore through a bakery in central Paris on Saturday, according to Paris' prosecutor.

Officials earlier said four people had died, but revised down the toll without explanation.

The first responders killed were trying to save the lives of their colleagues and other victims of the blast, French Interior Minister Christophe Castaner said. More than three dozen people were injured in the incident and 10 people remain in critical condition, he said.

A woman is evacuated by firefighters after the explosion of a bakery on the corner of the streets Saint-Cecile and Rue de Trevise in central Paris on Jan. 12, 2019. Thomas Samson / AFP - Getty Images

At least one other firefighter remains in life-threatening condition, Castaner told French broadcaster BFMTV.

Spain's Foreign Minister Josep Borell tweeted that a third person, a Spanish national, was also killed in the blast.

A spokesman for the Spanish Foreign Ministry said that two other Spaniards, a man and a woman, are in critical condition. All three Spaniards were in Paris as tourists.

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Officials said firefighters were already responding to a call of a gas leak at the scene when the explosion struck. Paris Prosecutor Rémy Heitz said at a press conference that the incident was believed to be the result of the leak, and that its source was under investigation.

Emergency personnel help injured persons at the scene of an explosion at a bakery near Rue de Trevise in Paris on Jan. 12, 2019 Yoan Valat / EPA

The blast, which hit the French capital at around 9 a.m. (3 a.m. ET), triggered a fire. Police tweeted asking people to stay away and allow for emergency crews to access the area.

The bakery, on Rue de Trévise, is in a busy tourist area known for its theaters and is in walking distance from the flagship location of the popular French department store Galeries Lafayette. There are also many hotels and restaurants around the immediate site of the bakery.

The blast left the street covered in debris, and destroying the facades of adjacent buildings. Window shutters were ripped off their hinges and windows shattered, covering the area with glass. Vehicles were crushed and at least one was flipped over by the power of the explosion.

According to video and photographs from the scene, crews were busy evacuating people by ladder from upper levels of buildings along the street in the blast's aftermath.

Castaner visited the scene less than two hours after the blast and said more than 200 firefighters were engaged in the rescue operation.

"My first thoughts are with the victims and their families," he said in a tweet.

Staff and guests at the Hotel Pax Opéra a few blocks down the street from the bakery heard the blast, according to Francesca Perna, a front desk receptionist.

"Immediately police arrived to check what had happened," she told NBC News.

The hotel wasn't damaged, Perna confirmed, adding, "The guests asked me what's happened but here in our hotel, there's no problem, the situation is quiet."

More than 80,000 security forces had been deployed nationwide for the ninth straight weekend anticipating more anti-government protests sparked by the "yellow vest" movement.

Nancy Ing reported from Paris, and Linda Givetash from London.