The billionaire French tycoons who pledged hundreds of millions in financial aid to rebuild Notre Dame cathedral in Paris have not yet paid a penny toward the restoration of the national monument, according to church and business officials.

Key points: Notre Dame's wooden spire, a masterpiece, and roof were lost to the fire in April

Notre Dame's wooden spire, a masterpiece, and roof were lost to the fire in April French tycoons publicly pledged hundreds of millions in donations after the inferno

French tycoons publicly pledged hundreds of millions in donations after the inferno They said they were now waiting on redesign details and a 'vision' before committing their funds

Instead, it's mainly American and French individuals, via Notre Dame charitable foundations, that are behind the first donations paying the bills and salaries for up to 150 workers employed by Notre Dame since an April 15 fire devastated its roof and caused its masterpiece spire to collapse.

This month they are handing over the first private payment for the cathedral's reconstruction of $5.8 million.

"The big donors haven't paid. Not a cent," said Andre Finot, senior press official at Notre Dame.

"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."

The fire claimed the cathedral's 19th-century wooden spire and roof. ( Reuters: Philippe Wojazer )

More than $1 billion was promised by some of France's richest and most powerful families and companies, several of whom sought to outbid each other, in the hours and days after the inferno.

It prompted criticism that the donations were as much about the vanity of the donors wishing to be immortalised in the edifice's fabled stones than the preservation of France's heritage.

Francois Pinault of Artemis, the parent company of Kering that owns Gucci and Saint Laurent, promised $163 million, while Patrick Pouyanne, CEO of French energy company Total, said his firm would match that figure.

Bernard Arnault, CEO of luxury giant LVMH that owns Louis Vuitton and Dior, pledged $327 million, as did the Bettencourt Schueller Foundation of the L'Oréal fortune.

None of that money has been seen, according to Mr Finot, as the donors wait to see how the reconstruction plans progress and fight it out over contracts.

Wearing hard hats to mass

The first stone of Notre Dame de Paris was laid in 1163, with the iconic building becoming the most famous of the Gothic cathedrals of the Middle Ages and one of the most beloved structures in the world.

A group of about 30 people will gather at the cathedral on Saturday evening (local time) to celebrate the first mass since the fire.

The service will be led by Paris Archbishop Monsignor Michel Aupetit in a small chapel near the garden, which used to hold the crown of thorns relic.

Participants will have to wear safety helmets, as the site is under construction to consolidate the structure.

The service will mark the anniversary of the consecration of the cathedral's altar, French media reported, which is celebrated each year around June 16.

It will be a "simple service", Notre Dame's chief priest, Monsignor Patrick Chauvet, told French broadcaster BFM TV.

Attendees will include several Notre Dame priests along with selected journalists and camera operators, with the mass to be broadcast on French television.

The diocese is waiting on approval from civil authorities to reopen space on front of the cathedral to the public, according to France 24.

If granted, evening prayer services could resume in Notre Dame square.

Americans form bulk of donations paid so far

Initial funds have been directed to critical conservation work detailing 19th-century elements that were lost. ( US Library of Congress: Charles Marville )

The reality on the ground at Notre Dame is that work has been continuing around the clock for weeks and the cathedral has had to rely partly on the charity foundations to fund the first phase of reconstruction.

The Friends of Notre Dame de Paris was founded in 2017 and its president, Michel Picaud, estimates that 90 per cent of the donations it had received had come from American donors.

Indeed, Mr Picaud just returned from a fundraising trip in New York.

"Americans are very generous toward Notre Dame and the monument is very loved in America," Mr Picaud said.

"Six out of our 11 board members are residents in the US."

Companies want 'vision' before funds commitment

A spokesman for the Pinault Collection — owners of Gucci and Saint Laurent — acknowledged that the Pinault family hadn't yet handed over any money for the cathedral's restoration, blaming that on a delay in contracts.

"We are willing to pay, provided it is requested in a contractual framework," said spokesman Jean-Jacques Aillagon, adding the Pinault family plans to pay via the Notre Dame foundations.

The roof and spire lost to April's inferno were only added to the church in the late 19th century. ( Flickr: Oli4.D )

The LVMH Group and the Arnault family said in a statement they were signing an agreement with Notre Dame's foundations and "the payments will be made as the work progresses".

Total has pledged to pay its $163 million via the Heritage Foundation, whose director-general Celia Verot confirmed that the multinational company had not paid anything.

She said donors were waiting to see what the plans were, and whether they were in line with each company's particular vision before they agreed to transfer the money.

"How the funds will be used by the state is the big question," Ms Verot said.

"It's a voluntary donation, so the companies are waiting for the Government's vision to see what precisely they want to fund."

While the clean-up and consolidation work now underway at Notre Dame is hugely important, it does not fit that description, said another foundation official, speaking on condition of anonymity.

The Bettencourt Schueller Foundation said it, too, had not handed over any money because it wanted to ensure its donation was spent on causes that fit the foundation's specific ethos, which supports craftsmanship in art.

Olivier de Challus, one of the cathedral's chief guides and architecture experts, said one of the reasons the rich French donors had not yet paid was that there were still so many uncertainties about the direction of the reconstruction work.

Mr De Challus said architectural experts were using digital models to try to establish how much damage the fire did to the cathedral's 13th-century stone, and whether its structures were fundamentally sound.

"It doesn't matter that the big donors haven't yet paid because the choices about the spire and the major architectural decisions will happen probably late in 2020," he said.

"That's when the large sums of money will be required."

Donations so far have gone to lead clean-up

Workers have sought to secure the site from rain damage. ( AP: Michel Euler )

While the billionaire donors delay signing their checks, the workers at the cathedral face the epic task of cleaning up the lead poisoning that has become an issue for the Parisian island on which Notre Dame is located.

An estimated 300 tonnes of lead that made up the cathedral's roof melted or was released into the atmosphere during the fierce blaze, sending out toxic dust.

The city's regional health agency says high levels of lead are now present in the soil of the island, the Ile de la Cite, and in nearby administrative buildings.

It has recommended that all pregnant women and children under seven living nearby take blood tests for lead, after an abnormally high level was detected in a child in the area.

Two dedicated workers have been cleaning the toxic lead dust from the cathedral's forecourt for weeks, and up to 148 more have been cleaning inside and outside the edifice as well as restoring it, according to Mr Finot.

Workers are building a wooden walkway so they can remove 250 tonnes of burnt scaffolding that had been installed before the fire for the ill-fated restoration of Notre Dame's spire.

They will then replace the existing plastic protection with a bigger, more robust umbrella roof.

After that, they will begin reconstructing the roof and vaulting.

Mr Finot said this process would take months and would be paid for in part by the Friends of Notre Dame and other foundations.

Architect David Deroo published this concept as a warning against an international design competition. ( Supplied: David Deroo )

Meanwhile, the French Parliament was slowly debating amendments to a new law that would create a public body to expedite the restoration of the cathedral and circumvent some of the country's famously complex labour laws.

French President Emmanuel Macron has said the work should be completed within five years — a deadline many French architects say is overly ambitious.

Mr Macron has appointed former army chief General Jean-Louis Georgelin to oversee the reconstruction.

ABC/wires