A lift carried workers into the middle of the tangled mass of some 40,000 tubes for a last evaluation, before others will be lowered by ropes from a crane overhead to start sawing apart the scaffolding this week, officials said.

The operation is one of the riskiest undertaken during the restoration work, since the 40 tonnes of fused metal must be removed without further damaging the limestone walls supporting the gothic vaults.

The scaffolding had been installed for a renovation of the steeple that was being carried out when the blaze erupted on the evening of April 15th, 2019.

“In an operation like this, it's like preparing a rocket launch, with final 'check-up' before the rope-access workers,” said Christophe Rousselot, director general of the Fondation Notre-Dame, the charity that is overseeing the collection of donations to the cathedral.

Millions of people around the world watched as the blaze tore through the church's roof, causing its steeple to collapse and sending billowing fumes containing toxic molten lead into the air.

Firefighters worked throughout the night to keep Notre-Dame from collapsing completely, though officials have said the structure remains at risk.