Technology stocks helped propel the nine-year bull market. Optimistic investors piled into the shares, hoping to grab a piece of the profits from industries such as social media, autonomous driving, video streaming and artificial intelligence.

Now, that confidence is evaporating.

Investors pummeled technology company stocks again on Tuesday, knocking the Standard & Poor’s 500-stock index down 1.7 percent. The Nasdaq composite, laden with technology stocks, sank 2.9 percent after a flurry of bad news about specific companies metastasized into a broad retreat from technology stocks.

The sell-off was ignited when the chip maker Nvidia said it was suspending tests of its self-driving car technology after an autonomous Uber vehicle struck and killed a pedestrian in Tempe, Ariz., last week. Nvidia has made supplying chips to self-driving vehicles a major part of its growth strategy, and Uber had selected Nvidia to outfit its fleet.

The news sent Nvidia shares plunging 7.8 percent, the sharpest decline of any company in the S.&P.

Shares of Tesla, a maker of electric-powered vehicles, also were in free fall, plunging 8 percent plunge after the National Transportation Safety Board said it was investigating a fatal crash last week involving a Tesla vehicle in California. The board said it was unclear whether an automated driving system was operating at the time of the crash.