US stock indexes end mixed; Nasdaq slumps on big tech slide

Major U.S. stock indexes ended mostly lower Monday amid signs that the Trump administration is laying the groundwork to ratchet up scrutiny on some of the market's biggest names: Apple, Facebook, Amazon and Google.

Google's parent Alphabet lost 6.1% and Facebook sank 7.5%. Apple shed 1% on the day that the iPhone seller kicked off its annual software showcase. Amazon fell 4.6%. The four have a combined market value of nearly $3 trillion, and their losses helped tilt the S&P 500 lower on a day when there were actually more gainers than losers in the stock market.

Investors were reacting to media reports suggesting that government regulators are setting the stage for...