The explosion destroyed two buildings, including a fashion school.
French Interior Minister Gerard Darmanin said the four injured were in a critical condition.
About 70 fire engines and 230 firefighters worked to extinguish the blaze by Wednesday afternoon.
Paris police chief Laurent Nunes said at the scene that ambulance crews were searching the rubble for other possible victims.
“Firefighters managed to prevent the fire from spreading to two adjacent buildings, but the explosion made them very unstable and they evacuated,” Nunez said, according to Al Jazeera.
The mayor of Florence Berteau said the explosion was “devastating”, with shards of glass falling from the building.
The cause of the explosion was not clear.
Paris prosecutor Lauré Becueau said early signs that the explosion originated from inside the building.
Investigators will check whether the condition of the building violates regulations, whether someone has caused an accident, etc.
Paris police immediately launched an investigation to determine the cause of the explosion in Paris.
Police are investigating a suspected gas leak that caused the building's facade to collapse.
Two people are still missing and may have been trapped in the rubble as search and rescue teams are searching for them.
A Paris police official said on Wednesday (21 June 2023), citing 9 News, that “the facade of a building in the 5th arrondissement has collapsed and ambulance crews are still checking to see if there are people inside.” .
Sirens blared as ambulances passed through the neighborhood, but residents began to move freely again along the previously closed rue Saint-Jacques.
Associated Press reporters said smoke had stopped coming from the building where the explosion occurred.