Forensic probe at Notre Dame begins

Forensic police on Thursday started sifting through the debris of the fire at Paris's Notre Dame cathedral as investigations continue into the cause of the blaze.

One theory under investigation is whether the fire was caused by a short circuit. The blaze was discovered near electricity cables running to the cathedral spire, reports say.

Investigators are also considering whether a fault in the alarm system meant firefighters were not called until it was too late.

An alarm was triggered at 6.20pm, but a security sweep of the area failed to discover anything untoward. The fire was only discovered when a second alarm was triggered 23 minutes later. By this time, the flames were reportedly several metres high.

Meanwhile, the company that was erecting scaffolding at the site has confirmed that some of its workers had been smoking, but has insisted the discarded cigarettes did not cause the fire.