A discarded cigarette, still alive with smoldering tobacco, is one of the most likely causes of the historic fire that saddened millions around the world and destroyed large parts of the historic Notre Dame Cathedral in Paris.

In a preliminary report Wednesday, investigators say they found no evidence of arson after weeks of interviewing 100 witnesses and sifting through tons of blackened debris and some 1,200 possible clues. A judicial inquiry will continue the probe.

The investigators said the most likely causes of the massive blaze are a lone cigarette or possibly an electrical spark from wires being used in an existing restoration effort underway when flames broke out in late afternoon of April 15.

Although seriously damaged with repairs likely to cost hundreds of millions of dollars, this was not the worst thing to happen to the 850 -ear-old cathedral. Construction began in 1163 and was completed in 1345.

It’s been the site of coronations including Napoleon’s and funerals like Charles deGaulle’s and marriages, including Mary Queen of Scots to her first husband Francis in 1558.

Notre Dame has been plundered and sacked including during the French Revolution as a symbol of royalty and the ancien regime. It was remodeled at one point to remove an entrance arch so a horse-drawn carriage could enter and save some royals a few steps. Several German shells inflicted World War I damage.

In 1909, almost 500 years after being burned alive by the English as a heretic, Jean of Arc was beatified there.

But fire, like April’s that fed on the ceiling’s 800-year-old oak beams, has been an infrequent intruder. According to Emily Guerry, a medieval historian:

Gothic cathedrals rarely catch fire. In fact, the Gothic style – with its powerful stone vaults and elegantly pointed arches – developed as a sort of flame-retardant system to protect cathedrals from fire.

The Gothic architectural style first appeared in and around Paris in the mid-12th century and became popular across Europe after a number of Romanesque churches succumbed to incendiary destruction, due in part to the high risk of older barrel vaults made of wood.

In fact, she noted, that after fire collapsed Britain’s Romanesque Canterbury Cathedral in 1174, monks invited French masons to rebuild their church in the fire-resistant Gothic style.

French President Emmanuel Macron has vowed to rebuild the cathedral within five years, estimated by architects to be an extremely optimistic view.

Meanwhile, workers are dismantling some 50,000 sections of pipe scaffolding erected for the pre-fire renovation. According to Notre Dame officials, the 15-hour fire heated some pipe sections to nearly 1,500 degrees.