I don't know that much about it but I did do a bit of research some time ago.
Look at this link, you may find it of some interest. However, you do have to be eligible to become a polish citizen in order to claim. The headline is misleading because it covers Jewish and non Jewish alike (as you read further down). Trying to google stuff like this can take forever. Maybe other forum members have some more information ?
I'm not trying to claim the land - I would just like to know more about the area - Karlowicze near Drohiczyn, farm number 12...
Sorry just seen your second post :(
You don't need to apologise if you do want to claim. Why should you ? There are plenty of people who will or have claimed as far as I can see.
Googling an area will give you some good sites for the info you want.