Wierd thumping noise?

[2002 v6 camaro uncharged]

I have a thumping noise coming from (I think) from the rear of the car. I have no shaking or vibration what so ever while driving. This driving was of speeds up to 60MPH. I have not been on the express way yet to see if I get any vibrations at higher speeds.
Any ideas what could cause this?
Oh yea, I did have a flat awhile ago and got it fixed but I did not notice anything right away so I don't think that would cause it. I also have a slow leak on another rear tire but I still hear the thumping noise even right after I fill the tire.

[StrtRacer98]

if you recently had a flat fixed theres a possibilty that the technician left one of his tools inside of the tire, that is bouncing around now.. it happens but if not that im really not sure.

[SpeedingFirebird]

If the tire shop used fix-a-flat (instead of actually patching the tire), this could cause a thumpming noise. fix-a-flat after it dries becomes big clumpy balls of crap.