French authorities believe they have two possible answers for how the Notre Dame cathedral caught fire in April. And it may all come down to a single cigarette.

Paris prosecutor Remy Heitz told reporters this week the cause of the fire was likely due to negligence, which could mean the flick of a cigarette at the wrong place, or a simple electrical misalignment. He added that the team hasn’t completely ruled out criminal activity, though the preliminary investigation into the April blaze found no sign the fire was started deliberately.

"Several hypotheses have caught the attention of the investigators, including that of a malfunction in the electrical system or that a cigarette that was not properly put out could have started the fire," Heitz said. "Even if certain failings, which may explain the scale of the fire, have been brought to light, the investigations carried out to date have not yet been able to determine the causes of the fire.”

However, just because they’ve narrowed down what they think caused the fire doesn’t mean the investigation is any closer to being completed. Richard Marlet, former head of the scientific police in France, told Euronews the team would still need to find which tiny electrical wire sparked the massive fire.

"It might be wires connected to the tools used by the companies in charge of renovation works," he said, or "it might also be the electrical circuit connected to the bells."

The team, HuffPost reported, came to this narrowed down conclusion after looking at more than 1,000 pieces of evidence and interviewing more than 100 people.

As CNN noted, Hertz additionally told reporters, a judicial investigation would only be carried out against a single person or entity "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."

Image zoom Chesnot/Getty Images

Beyond the investigation as to why the fire happened it appears the rebuilding efforts have hit a snag as well.

On Wednesday, the Notre Dame Foundation revealed its Cathedrale de Paris Fund has raised 396 million euros in donations and pledges to date. However, HuffPost reported, actually delivered donations to pay workers for the rebuilding efforts is actually only at 38 million euros. And even that money came down to small donations from across the world, not the billionaires who promised big bucks to rebuild.

“The big donors haven’t paid. Not a cent,” Andre Finot, senior press officer at Notre Dame, told the AP. “They want to know what exactly their money is being spent on and if they agree to it before they hand it over, and not just to pay employees’ salaries.”

So who’s really paying up? According to the foundation, 90 percent of the donations it received have come from American donors.