Nasdaq slumps to worst day since July; S&P 500 dips

U.S. stocks closed mixed on Monday as the tech sector dragged the Nasdaq to its worst day since July and kept the S&P 500 near the unchanged mark as investors cleared the decks for Alibaba's debut planned for later this week.

The Nasdaq Composite dropped 48.7 points, or 1.07 percent, to 4,518.90. The decline for the Nasdaq marked its biggest drop since July 31, according to Reuters.

Alibaba's could be the largest initial public offering in history and has seen "overwhelming" interest, according to the report.

Read more from Reuters.