After a month or so, they pulled all of the metal roofing out to take to recycling. The recycle center would not accept the metal. Turned out while in the ground with the hot ashes, it had become radioactive enough to trigger their Geiger counter. They told him to bring it back in a year as it would probably be safe enough for them to accept.
They told him that is happens a lot with metal they get that has been under ground for a length of time.
I had never heard of such a thing.