Wall Street tumbles on China concerns

NEW YORK (Reuters) - U.S. stocks opened lower on Friday, with investors concerned over reports of a regulatory crackdown on over-the-counter margin trading in China, a move that potentially would be negative for a recent flow of money into Chinese exchanges.

The Dow Jones industrial average <.DJI> fell 113.71 points, or 0.63 percent, to 17,992.06, the S&P 500 <.SPX> lost 10.3 points, or 0.49 percent, to 2,094.69 and the Nasdaq Composite <.IXIC> dropped 42.52 points, or 0.85 percent, to 4,965.27.

(This story removes extraneous letters in the first paragraph)

(Reporting by Ryan Vlastelica; Editing by Bernadette Baum)