At least seven people are in critical condition after an explosion ripped through a busy street in central Paris, sparking a fire in at least one building.
Paris police said nine other people were also injured in the blast in the Latin quarter, and emergency services were working to establish whether anyone was still inside.
The facade of a design school popular with foreign students collapsed, blowing out windows and starting the huge blaze.
“The explosion was extremely violent,” Florence Berthout, mayor for the area where the explosion happened.
She said four people were in “absolute emergency” condition and described pieces of glass still falling from buildings close to where it happened in the Rue Saint-Jacques, in the fifth district.
More than 200 firefighters were involved in the emergency response and were seen hosing down buildings, while Parisians posted images on Twitter of a huge plume of smoke visible across much of the city, including over the domed Pantheon monument.
Journalist Olivier Galzi told BFM TV that he had seen the facade of a nearby building “completely collapse”.
Police urged people to avoid the area, which was busy with tourists and foreign students, and a number of buildings were evacuated.
The neighbourhood, close to the Jardin du Luxembourg and the Sorbonne University, was cordoned off and scores of emergency workers filled the area.
“This is chaos,” said Christopher Gaglione, who said he witnessed the scene.
“I heard a huge explosion,” said local bar employee Khal Ilsey. “And as I was leaving the restaurant, I saw flames at the end of Rue Saint-Jacques.”
Art historian Monique Mosser said: “I thought it was a bomb.” Many of the windows in her building had been blown out by the blast’s shockwave, she said.
“A neighbour knocked on the door and told me that the fire brigade were asking us to evacuate as quickly as possible. I grabbed my laptop, my phone. I didn’t even think to take get my medication.”
Paris prosecutors said a probe had been opened into “aggravated involuntary injury”, and investigators were examining whether safety rules had been broken.
Local officials attributed the blast and blaze to a gas leak, but police spokeswoman Loubna Atta said it was too early to determine the source of the fire and could not confirm it was a caused by a gas explosion.
The building where the explosion happened was a private school, the Paris American Academy, which was founded in 1965 and teaches fashion design, interior design, fine arts and creative writing.
The smell of smoke lingered in the air while the plume of smoke started to clear as firefighters battled the blaze.
At around 6.40pm local time, Paris police chief Laurent Nunez said the fire was under control.
A blast in January 2019 in the ninth district killed four people and left dozens injured.
Reuters and the Associated Press contributed to this report.