No indication of its being retaliation as yet. Lots of confusing and conflicting stories, but these look reliable:
Calais Action
We have been hearing a lot of reports out of Calais about a fire, and just want to put your minds at ease: our sources indicate that there was a small fire that got out of hand, it appears to have destroyed around 40 homes but no-one was injured.
We will of course keep our eyes on the ground for any developments.
https://www.facebook.com/calaisaction/posts/1057479410971230
Caroline Gregory is a journalist and volunteer at the Calais Jungle camp.
Other reports now say the fire's been extinguished. About 40 homes lost, though.