Workers at the Notre-Dame cathedral in Paris yesterday began the delicate task of removing tonnes of metal scaffolding that had melted during a fire last year that destroyed the monument's roof and spire, an Agence France-Presse journalist at the scene said.

A lift carried workers into the middle of the tangled mass of some 40,000 tubes for a last evaluation before other workers will be lowered by ropes from a crane overhead this week to start sawing apart the scaffolding, officials said. The operation is one of the riskiest in 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 when the blaze erupted on the evening of April 15 last year, tearing through the cathedral's roof, causing its steeple to collapse and sending billowing fumes containing toxic molten lead into the air.

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