Termite activity and they will make their way through just about anything!

Termite issues and Post Tension slabs. The main thing to know is you cannot drill or cut into the floor without great risk, these cables are under extreme tension and could hurt someone. The great thing is that the termites can generally only come in from the exterior edge of the slab, with exceptions. The pictures at the top indicate a crack which allowed the termites to gain entry and this is rare.   

This was some padding put under a wooden floor in the home, the weirdest thing was that this was a Post Tension slab.