A plume of smoke rose above central Paris on Wednesday after witnesses reported hearing a large explosion.

Four people were left in critical condition after the blast, police said, with at least 33 more injured. First responders are still looking for at least two people still reportedly missing.

"[Fire crews are] going through the rubble looking for these two missing people, but also other possible survivors," said DW's Lisa Louis in Paris.

Nearby buildings — the windows of which had been shattered by the blast — were evacuated by the authorities.

French President Emmanuel Macron offered his condolences, saying: "Our thoughts are with those affected by the explosion in Paris, with the missing people, as well as with the rescue workers who are on duty."

What do we know about the fire?

Witnesses and local reporters said that they had seen the facade of a building collapse in the French capital's 5th arrondissement, also known as the Latin Quarter.

The building was on the Rue Saint-Jacques, a road leading from the Notre-Dame de Paris cathedral — which itself suffered a devastating fire four years ago — to the Sorbonne University.

"Authorities have been saying that some of the buildings around the one building where it happened are rather fragile," Lisa Louis said. "There are really old buildings here from the 16th, 17th, 18th  century and they are not up to standard."

"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."

Florence Berthout, the local district mayor, said that the building that had been hit by the blast was a private fashion school — the Paris American Academy.

Hundreds of firefighters deployed

Interior Minister Gerald Darmanin told people to avoid the area and not get in the way of the massive police and firefighter deployment.

Darmanin also said that a total of 325 firefighters had been deployed, while soldiers were reportedly on the scene to cordon off the site.

The city's mayor Anne Hidalgo said that a crisis center had also been set up. "My thoughts go first and foremost to the victims and their loved ones," she added.

Paris police chief Laurent Nunez said the "fire is under control" but had not yet been extinguished at the time of the statement.

Firefighters "prevented the spread of the fire to two adjoining buildings which were seriously destabilized by the explosion" and "were evacuated" Nunez added.

The cause of the blast was not immediately known, although local officials suspect it may have been caused by a gas explosion.

The Paris prosecutor's office said it was still too early to determine the origin with certainty.

ab/rs (Reuters, AP, AFP)