Fire early Tuesday morning at the American Walnut manufacturing facility at 2801 South Second in south St Joe caused an estimated 100-thousand dollars damage.  Authorities will say the cause of the fire will remain undetermined after investigation.  St Joseph Fire Department Inspector Rob Blizzard says the fire was confined to a trailer and the building it was housed in, as well as some tools and product.  Blizzard says he was unable to access the actual point of origin of the fire, because the floor of the raised trailer had collapsed.  There were no injuries.