If you are not local, then you will have to put on a sleuth hat. Have you tried taking to the previous owner or the real estate agent about the property? You can try calling the Tax Assessors Office and ask if they have any information on the tanks since they should be subject to advalorem/personal property. Have the tax parcel number available. If there is a near by neighbor, contact them to take a picture of the tanks and email to you. There should be information posted at the tanks (sign) to tell you who is the owner.