A cigarette or an electrical malfunction could be the reason behind the tragic fire that erupted at the Notre Dame Cathedral in April, French prosecutors said on Wednesday.

According to a statement issued by Paris prosecutor Remy Heitz, a first investigation into the fire showed no signs that it was intentional.

"If certain failings -- which may explain the scale of the fire -- have been brought to light, the investigations carried out to this date have not been able to determine the causes of the fire," Heitz stressed.

He added that the judicial investigation would be carried out "on the grounds of involuntary damage by fire due to a manifestly deliberate breach of a duty of care or safety imposed by law or regulation, which occurred under conditions likely to expose persons to bodily harm."