A question about the chimneys

This is a fantastic film. I thought the casting was a bit odd just because of films I relate the actors to.

Did the cremation chimneys really have flames coming out of the top like that? I'd have thought that it would just be smoke and an awful odour.

I've seen documentaries before of the local population being interviewed after the war was over saying there was always burning (witnessed as the smoke) and awful smell but I don't remember anything about flaming chimneys

Is this just a Hollywood embellishment ?