I have a fire case with total loss of a large metal building and all content. Defendant (co-tenant) has filed for summary judgment claiming we cannot establish causation. All experts, including defendant's, agree that origin was in defendant's half of the building and that because of the extent of the fire, specific cause will never be known. They all also agree that two potential causes were in exact area of fire origin: (1) extension cord running (in violation of National Electric Code) through metal skin of the building and showed evidence of faulting; and (2) history of defendant's employee smoking right before fire started. Under NFPA 921, because there is more than one potential cause, fire has to be listed as "undetermined." My cause/origin and electrical engineer experts (and other investigators) have testified that we know one of the two causes but can't say either one qualifies as "probable" (51% or greater) under NFPA 921 because of the extensive fire damage.