I had this happen on a Wal-mart 29'er rim(I did not buy the bike at Wal-mart). The pos had so many pieces of metal from when they pierced the spoke holes it sounded like a maraca. Nice if your into mariachi music, not so nice on a bike wheel. I took off the tire, tube and rim strip and shook shook shook it til they stopped coming out of the valve hole. of course this was a schrader valve, a presta with the small hole might take more shaking.
Good Luck