The Paris police cited the result of tests showing that the frame of the renowned cathedral as well as its iconic spire had discharged particles of the noxious metal following the 15 April blaze that engulfed Notre Dame.
According to the probe, lead was found in areas adjacent to the cathedral, noting that it was "very localised" and "notably on premises that may have been standing open at the time of the fire, and where dust had settled".
The police played down the threat of contamination as the detrimental effects of lead poisoning manifest themselves over years of exposure to the toxic metal.
The police added that public areas under threat for potential lead contamination have been shut down and will not be reopened until lead levels stabilise.
The announcement comes as the French environmental campaigners, Robin des Bois, reported that some 300 tonnes of lead from Notre Dame's roof and spire had melted in the conflagration. The group called on the authorities to detoxify the debris produced in the disaster.