Soot in oven operating on propane.

I have read two threads on the subject, but still need more help - badly! I have an older gas stove, of which I use only the oven. The oven has worked great for years - until I had propane delivered on November 24. The next time I used it, to roast the Thanksgiving turkey, the roaster became absolutely covered with soot. My hands turn black if I touch it. When I took the cover off for a short time to brown it, the turkey turned grey with soot. I had a frozen dinner tonight (no touching that roaster!), and before I put it in, tested the pan I always put the dinners in. There was NO soot that came off on my hands. After heating the dinner, the pan was covered with soot and there were black, sooty marks on my hands from the little I touched it. The new propane delivery was the only change. Is it possible they delivered something else (they added 55 gallons; there were 45 in the tank) or that the propane was contaminated with something else, such as furnace oil? The company sells both oil and gas. HELP! :eek: (Please excuse if there is a duplicate. This did not show up at first, and it might not have gone through my slow connection.)