Rescue workers combed through debris in central Paris on Thursday, a day after a powerful explosion ripped through a building on the Left Bank and injured about 40 people, several of them critically.
The authorities in Paris said that one person was still unaccounted for after the blast, which rocked the French capital on Wednesday evening and damaged much of the building, which was on Rue Saint-Jacques, in the Fifth Arrondissement, leaving a pile of charred wooden beams and stone rubble.
Official information about the identities of the victims was not immediately available. But the building was home to a small fashion and arts school known as the Paris American Academy, and on its Facebook page, the school said that its president, Peter Carman, had been hospitalized in Paris after the explosion and was in critical condition and under anesthesia.
The medical status of three professors was still unknown, but most of the students appeared to be safe, the school said.
The building also hosted the headquarters of the General Secretariat for Catholic Education, an institution that promotes Roman Catholic teaching in France.
The explosion started a blaze that hundreds of firefighters quickly brought under control. Most of the injuries were minimal, but the Paris prosecutor’s office said on Thursday that six people were still in critical condition.
François Braun, the French health minister, told the BFMTV news channel that some victims suffered blunt-force trauma after they were thrown back by the blast, while others were injured by the flames.
“The most serious victims have extremely serious burns,” Mr. Braun said.
Prosecutors have opened an investigation into the explosion, whose origin was unclear. Foul play is not a leading theory, but the authorities have not confirmed suspicions that a gas leak was responsible.
Many apartment buildings in Paris use gas for heating and other purposes, and although deadly explosions because of leaks are uncommon, they are not unheard-of.
In 2016, an explosion caused by a gas leak in the Sixth Arrondissement tore off the roof of an apartment building and wounded 17 people.
Three years later, a gas explosion destroyed a bakery in the Ninth Arrondissement. That blast killed four people, including two firefighters, and injured dozens of others, raising questions about the safety of the French capital’s gas infrastructure and leading to a protracted investigation to determine the exact causes of the leak.
Reports by court-mandated experts in 2019 and 2020 faulted the Paris city government and the building’s property management company for failing to properly maintain the building and the sidewalk in front. Those reports said that a gas pipe had ruptured after the ground in front of the building started to sink, creating a dangerous pocket of gas.
The city government and the building’s property management company were both charged with manslaughter, but the case is continuing, and it is unclear if they will face trial. Last year, the city asked for a new report by a different group of experts, who have not yet revealed their findings.
Jean-Pierre Lecoq, the mayor of the neighboring Sixth Arrondissement, told Le Figaro on Wednesday that Paris’s gas network was “fragile” and very disparate, alternating between newly renovated sections and aging, dilapidated ones.
Different authorities are also in charge of maintenance — street pipes are handled by the city, for instance, while those inside a building are usually handled by property management — adding to uncertainty about the overall state of the network.
Under rainfall on Rue Saint-Jacques on Thursday, security forces were holding a perimeter around the area of the blast, which rattled Parisians, with the initial noise and chaos reviving memories of the deadly terrorist attacks that struck the city in 2015.
Some people who lived in several neighboring apartment buildings had still not been able to return after being evacuated as a precaution.
Florence Berthout, the mayor of the Fifth Arrondissement, told BFMTV that three children were among those lightly injured but that 12 students who were supposed to have been at the site had left that afternoon to visit an exhibit with their professor.
The Paris American Academy is a small school established in 1965 for students pursuing a career in arts or fashion. It describes itself as the French capital’s “first bilingual design school, located in the Paris Latin Quarter.”
Nine students at the academy were from Kent State University, in Ohio, and were in Paris for a monthlong fashion class. All of those students are safe and will return to the United States a few days early, the university said in a statement.
“We are thankful and relieved to know that our Kent State students are safe and accounted for,” said Todd Diacon, the university’s president. “This incident occurred later in the day and the students had left the building for an off-site activity. Our thoughts are with the other individuals who were injured in the explosion.”
Other French cities have also been hit by deadly gas-related explosions. In April, eight people were killed in the Mediterranean port city of Marseille after a violent blast destroyed a residential building.