Yes. Or rather, seven horcruxes (on of them an unknown accident) and an eighth shard in Voldemort's new body.
The shard that was released when his first body was destroyed was bound to this world by the existence of the horcruxes. It floated around alone until he and Peter somehow created the thing we saw in the beginning of GoF.

And yes, Colin and Dennis were muggle-born. See CoS, chapter six.