[Tomgs]

If you look at their description they are invisible to a level 5 scan. I don't know if you can get that high in the demo because I haven't bothered with scanners yet. I do hope that you will be able to detect them in the full Version with the appropriate technology. Of course its much quicker to research mines than the detection research would be so mines will be virtually undetectable for a long time in a low technology start.