Possible early signs of an infestation?

Hey guys,

I've got nine plants in my closet, 2 weeks into veg. Just transplanted them from potting soil into 1 gal. pots of Promix. They are doing nicely and have gone into a major growth spurt in their new pots.

However... I did notice some small flies flying around in the grow chamber, small black insects, too small to positively identify. I immediately pulled all the plants out to inspect the undersides of the leaves. I didn't see any egg casings or insect activity, but then again, I was using just eyesight. I gave them a foliar spray and put them back into the closet. I did notice some of the bugs landing on the surface of the soil and they went below the surface, into a crack in the soil near the side of the pot.

Is there anything kind of organic pesticide I can safely use on the plants at this point? Any idea what the insects are? Should I invest in a pocket microscope?

Any input would be helpful. Thanks. =)

put up a sticky strip also add a couple of hot shot pests strips sold almost everywhere this should help out.