Understanding Paris event from October 5?

This morning in Paris, there has been an enormous surge in PM10 / PM2.5 measurements, almost twenty-fold, that was very short (|1/4 hour) and also perfectly visible on the city service “Airparif” (the whole map basically switching from green to red).
The curve below gives you an idea.
I would like to know if anyone could point me to an explanation, as for instance Airparif just doesn’t talk about it…

in addition : surprisingly, the Airparif website now has eliminated the surge, that was still visible a couple hours ago. At this time, when you ask for the 9am visualization, it’s far cleaner, with just a barely-visible trace of red saturation along the ‘Autoroute du Nord’, circa “la plaine saint denis” area.

May I add I myself am located at the bottom right of this map, so definitely in the ‘green’ here (which was darn red this morning at that specific hour)

It was really on the live map of Airparif ?
Let’s check tomorrow with the archive.
I try to find sensors next to this location but no surge at 9am.
Can you give me the GPS location of your sensor?