Burn marks on the stairs below

Hi all,

I inspected one house and found some burn marks on the stairs below. I am wondering what casuing this. I looked around and I didn’t find anything excetp the marks. The stair was in the furnace room but far away from the furnace and water heaters and I touched the marks, they were smooth. Please advise and how will you tell the clients?



From what I can tell from the pictures, the burn marks occurred prior to
using them for the steps.

Yup, in total agreement!

I also agree