"Natural gas Fires hot enough to burn metal are suspect." I was thinking about other ways to ignite the fires. high pressure natural gas which wasn't added any Methanethiol (rotten egg odor) for people to detect. The high temperatures could be from the Alumina nano fibers (aluminium) they have admitted dumping out of airplanes in order to "remove hydrocarbon impurities"
https://en.wikipedia.org/wiki/Aluminium_oxide_nanoparticle#Application I've been looking into ways to detect Alumina nano fibers it's not easy. 254 UV light the fibers admit wave color. Though that is the same light frequency that creates Ozone. We physically can't be around that frequency of light it will burn us.
I'm guessing the best way. Would take a soil sample put it into dark box with a 254 UV light turn it on for a very short time to see it. Though I don't have a good answer.