It doesn't specifically say he made them, but it doesn't really say he didn't. The twisting of the Elves was definitely not creation, and weren't the Balrogs fallen Maia or something. (I'm not sure on the latter, so ignore me if I'm wrong)
But I like to think that he couldn't create, because that would completely revoke any power Eru had over the Vala. He created them, and if they could create, then they would be as powerful as He. So I believe that he could not create something from nothing.
And besides, if he could have created these beings, why didn't he just make millions of them and wipe everything else off of the earth?
Answer me that...