A young construction boss boasted about his firm's ability to protect historic sites when the company won a contract to repair the spire of Notre Dame.
Julien Le Bras, 32, declared last year: "Our first thought is to protect the values of historical buildings, it's in our DNA."
His firm, Le Bras Freres, a small company known as the 'Cathedral Restorers', had won the £5million (€5.8m) contract to renovate the spire of the Paris landmark.
Today craftsmen from the company were being questioned by investigators after the spire came crashing down in Monday's blaze, which caused such extensive damage that experts believe it could take decades to repair.
However the head of the group of companies for the Restoration of Historic Monuments, Frédéric Létoffé, predicted it will take between "10 to 15 years" to fully restore Notre Dame.
The site would need to be secured before any restoration work can take place.
"This will require a lot of work since, beyond shoring and reinforcement, it will be necessary to build a scaffolding with an umbrella to be able to cover the entire roof that went missing, to ensure protection against weathering."
Inferno started in roof cavity
Investigators believe the devastating blaze started in the roof cavity below the spire where the work, which included the use of electric tools, was being carried out.
The blaze was discovered at around 6.50pm but workers would reportedly have downed tools between 5pm and 5.30pm.
According to investigators, an alarm went off at 6.20pm, interrupting a Mass, but no fire was found. The alarm then sounded again at 6.43pm, by which time the flames were burning out of control.
The first daylight pictures inside the wreckage today showed the roof destroyed, the 850-year-old church exposed to the elements and the floor covered in charred debris.
However the three 'irreplaceable' Rose Windows - which date to the 13th century and were last night feared to have melted or exploded - are all still intact.
Other treasures, including a crown of thorns reputed to have been worn by Jesus at his crucifixion, were also rescued from the fire, which officials believe was started by accident.
Le Bras told reporters at the scene: "We want more than anyone for light to be shed on the origin of this drama."
He said his company has 12 workers involved in the refurbishment, though none were on site at the time the blaze began on Monday evening.
He insisted that "all the security measures were respected" and that 'workers are participating in the investigation with no hesitation.'
A hole is seen in the dome inside Notre Dame cathedral.
Various officials have suggested the fire could have been linked to the renovation work. Paris prosecutor Remy Heitz said the investigation was in its early stages.
The 32-year-old construction boss had previously heralded his firm's "technical ability and competence" and pride in restoring historic buildings.
In a film posted online, Le Bras said: "We are proud of our work on historic buildings. We have the technical ability and the competence for his work.
"Our first thought is to protect the values of historical buildings, it's in our DNA."
In the video posted on the Le Bras Freres Facebook page on New Year's Eve, the CEO says his firm is proud to have been chosen to work on buildings across France, including the Congress Palace in Metz and Notre Dame in Paris.
Filmed at the staff end-of-year party Le Bras said: "We are completely ready to start work in 2019 and we are very well motivated. The team is ready and we have the know-how."
And on winning the Notre Dame contact he said: "The goal is to keep as many old items as possible and not to put the building at risk."
Le Bras said he would ensure that Notre Dame's famous spire - known in French as la fleche - would not be damaged during the renovation work.
He said: "The spire is 105m tall and there is no question that we will put any pressure on it with the scaffolding."
The Notre Dame renovation work was estimated to cost a total of £130 million (€150 million, in an audit by the French Ministry of Culture in 2014. Restoring the famous La Fleche spire to its former beauty was estimated to cost £5 million (€6 million) alone.
Established in 1954 by Louis Le Bras, the current CEO's grandfather, Le Bras Freres, which is based in Jarny, Lorraine, in the east of France and employs 200 craftsmen, has been trusted to renovate some of France's most historic buildings.
The firm won the contract to restore Notre Dame last year after successfully renovating nine other historic sites including cathedrals in Reims, Poitiers, Verdun, Strasbourg, Amiens and the Pantheon in Paris.
Restoration work on Notre Dame, which began in July 2018, was set to be carried out in several phases over 20 years.
The series of repairs and restorations included attention being paid to the 100m meter high spire and the 12 apostles that crown it, which were said to have a large number of cracks and fissures.
The fire raged for several hours and more than 400 firefighters battled the blaze.
Experts found that the ageing stonework of all of the flying buttresses were causing problems for the stability of the whole building and many pinnacles and gargoyles were in disrepair or had fallen.
Lead framework of the stained glass windows had also become weakened.
Work using electric tools had been going on in the roof, but the fire caused the iconic spire to collapse. It comprised 250 tonnes of lead and stood 315ft tall.
After winning the contract Le Bras said: "No one has touched it [Notre Dame] for 150 years, it's a great honour to be doing the work.
"We are not expecting our work to last ten years but we are aiming it to last for another 150 years!" he joked.
The CEO explained to staff that the tender for the restoration work had been split into three – the scaffolding, the frame and the cover.
And he was ecstatic when the "small company from Jarny, eastern France, won against large international groups!".
He added: "This will be our tenth cathedral. This family business has worked on another high-profile buildings in Paris, the Pantheon."
The firm boasts that it is proud to employ French workers and has refused to take on 'low-cost' staff from abroad.
Le Bras recently invested €5million in new machinery and work space at his headquarters in Jarny, in the department of Meurthe-et-Moselle, in the Lorraine region of eastern France.
The Paris prosecutor's office is probing 'involuntary destruction caused by fire', indicating authorities are treating the blaze as a tragic accident and not arson or terrorism.
"Nothing suggests that it was a voluntary act," Remy Heitz told reporters outside the Gothic cathedral, adding that the workers employed at the site were being questioned over Monday's blaze.
Heitz also revealed that an earlier alarm had gone off at 6.20pm, interrupting a Mass, but no fire was found. The alarm then sounded again at 6.43pm.
