Unknown Water

For five days I have been trying to find out where the water has been coming from in my basement.

I checked the pipes for leaks..... Good
I checked for spilled water...... Good
I checked to see if the dishwasher was leaking.... Good
I checked all the walls for a leak..... Good
only conclusion is that it is coming up from the floor. This is very strange since it is not on the bottom floor and there are no pipes or drains. Carpet keeps getting soaked in the middle of the room. Guess I will have to call a foundation specialist.