Officials from France's Ministry of Culture told Efe news that the decontamination work would take up to three weeks.
The cleanup will focus on the Notre Dame square, Rue de la Cité and Rue d'Arcole, which were closed off to traffic and pedestr.
When the fire ripped through the cathedral on April 15, hundreds of tonnes of lead melted, spewing toxic dust into the air.
Levels of lead remain exceptionally high at some spots inside the cathedral, and in the soil of the adjacent park as well as roads. Those areas have been closed to the public since the incident.
The Ministry of Culture said the decontamination units would use two cleaning methods the first one applying high-pressure detergents and the second using gel to absorb the toxic substance.
On July 25, repair work on the landmark was suspended after labour inspectors raised concerns about workers' safety. Renovations are now scheduled to resume on August 19.
Also in July, two schools in a neighbouring district were closed after worrying amounts of lead particles were detected.
Last week, workers sprayed a special gel onto the playgrounds at these two schools. The gel attracted the lead particles as it dried and was later removed, according to city authorities.
According to the report, decontamination should not affect the revamp as long as workers meet a set of requirements listed by Paris Perfect Michel Cadot in July.
Analyzers earlier recorded high levels of lead mainly in the roof and spire of Notre Dame that were damaged in the blaze.
( With inputs from IANS )