Officials confirmed in the evening that she had succumbed to her injuries.
The cause of the fire is still unclear. At around 2.20pm, a pedestrian noticed smoke developing on the top floor of an apartment building in Rue du Canal.
Firefighters entered the building and broke down the door, upon which they discovered the woman lying on the floor.
After several reanimation attempts, the rescue helicopter took her to hospital in Esch, where she died shortly after.
Another family also living in the building was unharmed. An autopsy will be carried out.
During the operation the surrounding roads were closed off.
