Comment by superkuh

There's a good chance that conflagrations during WWII generated such clouds. There are well established incidents of such in Germany (and Japan) (ref: https://journals.ametsoc.org/view/journals/bams/91/9/2010bam... , Hamburg, Dresden, etc) but nothing for certain in France. The British attacks on Royan which destroyed 85% of it with high explosive and napalam would be the most likely site.