at the scene have reported "many casualties", according to AFP. One of the injured is in a critical condition.
The explosion, which happened at around 11:15 am local time has destroyed 10 apartments in the four-storey building. Authorities have evacuated the area over fears of a possible second explosion and a security perimeter has been set up.
Mayor Adeline Hazan told the media in a statement that the explosion was probably caused by a gas leak, and she added that the blast was "very strong", and had shattered windows in other buildings.
A firefighter told the media, "There are many victims... We have very little information on the state of the victims."
have stated that there are fears some people are still trapped in the wreckage. More than 100 rescue workers, including bomb and gas experts and firefighters, are working on the scene.
at the scene show that an entire corner of the building has been destroyed. The apartment building was reportedly the oldest in the area and had been renovated several years ago.
Four people from the same family are said to be among the victims affected by the explosion. The father of the family, while injured himself, helped rescuers find his wife and child who were trapped beneath the debris, before tragically dying in an ambulance.
A resident of the housing project, 27-year-old Abdel Kader said, "The explosion was very strong, like a sonic boom from a fighter plane. We had been playing football on a field about 30 meters (100 feet) away, and ran to the scene."
"The building had fallen like a house of cards ... 30 seconds after that we saw a man calling for help, he was on a slab. His legs were caught. Later, he died," he added.
The office of French President Francois Hollande conveyed his condolences to the victims' relatives, stating, "The explosion of a residential building in Reims is a terrible drama."
this is the second gas explosion in Reims this month. On April 3, four members of one family were killed and another badly injured in a housing estate in nearby Witry-les-Reims.