A second person has died following a blast that collapsed a building in central Paris on June 21, a source close to the case told AFP Friday.

The woman had been seriously wounded as the structure fell, the source said, confirming a report from daily Le Parisien.

The first person killed in the explosion in the Rue Saint-Jacques in the French capital's touristic fifth district, also a woman, was found under the rubble six days later.

She was believed to be a teacher at the Paris American Academy, a private fashion school housed in the 17th-century structure that was a listed historic monument.

Around 50 people were also wounded in the blast, four of them seriously.

Paris investigators opened a probe on Monday into involuntary manslaughter and involuntary wounding by failure to respect safety procedures, a judicial source told AFP.

But the source added that further work would face the challenge of working around the ruins contaminated with lead and asbestos.

Eyewitnesses to the explosion have described smelling gas in the moments before it struck, blowing out shop fronts and apartment windows in a radius of 500 metres (yards).

Their testimony, as well as CCTV recordings, suggested that the explosion took place inside the building, prosecutors have said.

Around 60 evacuated families from the neighbourhood remained in emergency housing by Thursday, fifth district mayor Florence Berthout said.

Paris mayor Anne Hidalgo has said the city will provide two million euros ($2.2 million) in support for local businesses and residents.

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