An explosion tore through an apartment building in central Paris on Wednesday, partly collapsing the structure and injuring at least 37 people, four of them critically, according to the French authorities.
The explosion, which occurred around 5 p.m. on Rue Saint-Jacques, in the Fifth Arrondissement of the French capital, projected rubble and glass into the street and started a fire that sent black smoke billowing into the sky.
Gérald Darmanin, the French interior minister, told reporters more than 300 firefighters had deployed to the scene and were able to prevent the flames from spreading to neighboring buildings, which were nonetheless “destabilized” and evacuated as a precaution.
Mr. Darmanin said rescue workers were looking through the rubble late Wednesday for two missing people, although it was unclear whether they had been in the building at the time of the blast.
“It is therefore possible that we will find bodies overnight, or survivors,” Mr. Darmanin said.
The cause of the explosion, which rattled the neighborhood with a loud boom, was not immediately clear. Videos and pictures on social media appeared to show the top of the building blown off and the street below strewn with debris. The prosecutor’s office said it had opened an investigation.
Some witnesses told French media that they had smelled a strong odor of gas shortly before the blast.
“Many buildings need to be inspected to see if they are weakened or not,” Anne Hidalgo, the mayor of Paris, told reporters. “A lot of buildings have had their windows blown out,” she said, adding that some evacuees would have to wait before returning home.
Laure Beccuau, the Paris prosecutor, told reporters at the scene that the blast appeared to have started in the building itself, which sits on the corner of a semicircular plaza, next to the Val-de-Grâce church.
Ms. Beccuau said that investigators would try to determine whether the explosion was the result of individual negligence, noncompliance with building security rules or another cause. But the charges being considered by the prosecutor’s office — unintentional injuries — suggested foul play was not a leading theory.
Mr. Darmanin said that the building, which housed the offices of an American fashion school, was old but “did not exhibit any particular difficulties.”
“To our knowledge, there was no alert preceding the explosion,” Mr. Darmanin said.
Michel Denis, the head of a nearby music school, told Le Parisien that he was in a meeting in his office on the ground floor when he heard a sudden explosion, “like a bombing.”
“I was thrown back 3 meters, everything was thrown upward,” Mr. Denis said, adding that once he got outside, the street was filled with debris and panicking bystanders.
“The firefighters and police quickly arrived and evacuated us,” he said. “Thankfully it was the first day of vacation and there weren’t many people in our offices.”
The explosion came at a busy time in France: the Fête de la Musique, a national day of musical celebration where crowds around the country go to concerts or congregate outside to listen and dance to amateur street bands.
President Emmanuel Macron, who was hosting a concert that included musicians like Jon Batiste and Gregory Porter at the Élysée Palace, said that “tonight we’re celebrating music, but we’re not in the mood to party.”
“We are thinking of all those who have been hit by the explosion in Paris, of those who are missing, of the rescue forces who are at work,” he added.