PARIS, France (AFP)— An explosion of unknown origin that ripped through a building in a historic area in central Paris on Wednesday injured 24 people, including four seriously, officials said.

The blast was followed by a major fire which caused one building, housing a fashion school, to collapse, as well as an adjacent building, emergency services said.

Some 70 fire trucks and 230 firefighters were battling the blaze which was contained by the early evening. Nine doctors were also at the scene.

The fire service said there had been “an explosion” which had “caused the collapse of two buildings”.

Several witnesses told AFP at the scene they had heard “a giant explosion”.

Windows as far as 400 metres (440 yards) away were shattered, AFP reporters said.

The “violent” fire which broke out after the explosion has now been “contained”, Paris police chief Laurent Nunez said at the scene, adding that “work is still taking place under the rubble” to find any more possible victims.

Prosecutors said two people were still missing following the blast.

The firefighters “prevented the spread of the fire to two adjoining buildings which were seriously destabilised by the explosion” and “were evacuated”, Nunez added.

The blast was preceded by a gas leak, the district’s mayor said on Twitter.

Florence Berthout, mayor of the 5th district in central Paris, said the main building affected is a private fashion school adjoining the former Val-de-Grace military hospital.

According to the mayor, the noise of the “quite enormous” explosion spread “in part of the district”.

French prosecutors said the cause of the blast had not been determined. An investigation was launched immediately, they said.

Interior Minister Gerald Darmanin had earlier asked on Twitter for people to stay away from the area to not hinder the massive deployment of firefighters and police.

AFP pictures taken at the site showed tall flames, and smoke billowing from the building, situated at Place Alphonse-Laveran, close to the Luxembourg Gardens.

The area is at the edge of the Latin Quarter, a top tourism area in the French capital.

A local resident, speaking on condition of anonymity, told AFP that he “heard a huge explosion which made the windows vibrate”.

“I thought it was a bombing. It echoed in the apartment. I had 10 seconds of great concern, many people were at the windows,” he added.

While the cause is unclear, there are many precedents for gas-related blasts in the French capital.

The blast recalled a massive explosion that rocked Paris in January 2019, when a suspected leak in a buried gas pipe destroyed a building on the Rue de Trevise in the ninth district, killing four people including two firefighters.

The shockwave blew out scores of nearby windows, and dozens of families were forced to evacuate their homes for months. Much of the street still remains off limits four years after the disaster.

Paris city hall has been charged with involuntary manslaughter over that blast, and legal wrangling over the exact cause continues.