Scientists begin hunt for evidence on cause of Notre Dame fire

French police scientists have entered Notre Dame cathedral for the first time to begin gathering evidence on the cause of the fire that devastated the roof and destroyed the spire last week.

Three different agencies will begin to take samples and look for clues that might suggest how the blaze began and ripped through the centuries-old gothic architectural masterpiece last week. Police are treating the blaze as accidental.

It has taken 10 days to secure the cathedral structure to allow for a thorough examination of the charred interior. Investigators have already interviewed cathedral staff and workers who were carrying out renovations.

Police believe an electrical short circuit might have been at the heart of the fire. Investigators are expected to search through the fire-damaged cathedral for remains of cables, lights or parts of circuitry that might give clues, but DNA evidence could be complex to collect from the large fire site.

Investigators are also trying to establish whether all the correct procedures were followed at about 6.20pm last Monday when the first alarm went off at the cathedral. Staff reportedly made checks but did not see anything unusual until a second alarm sounded about 20 minutes later.

The scaffolding firm that had put up a vast structure of metal scaffolding on the Notre Dame for renovations admitted this week that some of its workers had smoked on the site, but ruled out that a cigarette butt might have started the fire that destroyed the cathedral’s oak-framed roof.

A spokesman for the family-owned Le Bras Frères said some workers for its scaffolding unit had informed police that they had “sometimes” smoked on the scaffolding, despite a smoking ban on the site.

“We condemn it,” the spokesman said. But he insisted the fire started inside the building and smoking was not to blame. “It was not a cigarette butt that set Notre Dame de Paris on fire.”