Wall Street is tumbling on fears the big U.S. companies that have feasted on the artificial-intelligence frenzy are under threat from a competitor in China.

Wall Street is tumbling Monday on fears that the market’s winners who have feasted on the artificial-intelligence frenzy are under threat from a competitor in China that can do similar things for much cheaper.

Wall Street’s superstars are tumbling Monday as a competitor from China threatens to upend the artificial-intelligence frenzy they've been feasting on. The S&P 500 was down 1.7% in afternoon trading and heading for its worst day in more than a month.