US stocks tumbled, sending the S&P 500 index to its lowest level since May 1, on concern technology spending will slow and second-quarter earnings will fail to justify a four-month rally.

The S&P fell 2 percent, or 17.69 points, to 881.03, while the Dow Jones industrial average sank 161.27, or 1.9 percent, to 8,163.6. The Nasdaq composite index slipped 2.3 percent, or 41.23, to 1,746.17 as Google traded under $400 for the first time in six weeks.

Microsoft and Google lost more than 2.8 percent.