By Sara Sjolin, MarketWatch , Ryan Vlastelica

Amazon slumps after results, offsetting Alphabet gains

U.S. stocks turned negative in afternoon trading on Friday, reversing their earlier gains after the Federal Bureau of Investigation said it was restarting a probe (http://www.marketwatch.com/story/fbi-restarting-probe-into-hillary-clintons-emails-2016-10-28) into Hillary Clinton's emails, adding a new dose of political uncertainty into the markets.

Major indexes had traded higher earlier in the session, supported by a strong GDP reading, but the news prompted a sharp turnaround and extended the week-to-date declines of the S&P 500 and Nasdaq.

The restarted probe came after FBI Director James Comey said he had learned of emails that "appear to be pertinent" to its investigation, though he added that the FBI "cannot yet assess whether or not this material may be significant." In July, Comey had said that charges against Clinton--who controversially used a private email server--weren't "appropriate."

Polls have strongly indicated that Hillary Clinton, the Democratic presidential candidate, will win out over Republican Donald Trump in next month's election, an outcome that analysts said markets had priced in.

"This throws such a monkey wrench into anyone's ability to predict what will happen over the next couple of weeks," said Wayne Kaufman, chief market analyst at Phoenix Financial Services. "Most people had been predicting a Clinton victory, and all of a sudden the waters are muddied again. Markets hate uncertainty more than anything else."

The Dow Jones Industrial Average slid 52 points, or 0.3%, to 18,118. The S&P sank 10 points to 2,123, off 0.5% on the day. The Nasdaq Composite Index lost 25 points, or 0.5%, to 5,190.

With the afternoon shift, the Dow lost its week-to-date gain. It is currently on track to close 0.2% lower for the week, while the S&P is set for a 0.9% drop and the Nasdaq is on pace for a weekly loss of 1.2%.

Market action on Friday was also driven by a number of high profile companies reported earnings since Thursday's close, results provided little in the way of a trend. Among energy companies, Chevron Corp(CVX) rallied while Exxon Mobil Corp.(XOM) fell, while in the tech sector, a rally by Alphabet Inc. (GOOGL), the parent company of Google, was offset by a sharp decline in Amazon.com Inc.(AMZN).

A preliminary read of third-quarter gross domestic product showed the fastest pace of expansion since mid-2014 (http://www.marketwatch.com/story/gdp-hits-29-in-biggest-gain-since-mid-2014-2016-10-28), with the economy growing 2.9%, in line with expectations. The report showed acceleration from the growth rate of 1.4% seen in the previous quarter.

The data was seen as doing little to change the view that the Federal Reserve would raise interest rates at its December meeting. The U.S. central bank has said it would raise rates when it deems the economy strong enough to withstand such a move.

The Fed is meeting next week, but expectations for a rate increase are low ahead of the Nov. 8 election. Instead, markets are pricing in a tightening at the December meeting, with the CME Group data showing an 83% probability of a hike in December.

In other data released on Friday, consumer sentiment unexpectedly dipped from the prior month.

Read:Get ready to cheer the best five days of the year for stocks (http://www.marketwatch.com/story/get-ready-to-cheer-the-best-five-days-of-the-year-for-stocks-2016-10-27)

Amazon was one of the biggest movers of the day, dropping 5.2% to $776.13 following disappointing earnings reported late Thursday (http://www.marketwatch.com/story/amazon-posts-smaller-than-expected-profit-increase-2016-10-27-164855144). While the e-commerce giant's revenue came in line with forecasts, earnings were below expectations.

On the upside, Alphabet rose 0.3% to $819.54 following stronger-than-expected earnings out on Thursday (http://blogs.marketwatch.com/thetell/2016/10/27/alphabet-expected-to-report-stronger-earnings-and-sales-live-blog/).

In the energy sector, both Chevron and Exxon reported sharp drops in quarterly earnings, hurt by weak oil prices. However, Chevron rose 3.7% as it nonetheless returned to profitability (http://www.marketwatch.com/story/chevron-returns-to-profit-though-revenue-slides-2016-10-28) following three straight quarters of losses. The stock was the biggest percentage gainer among Dow components. Exxon fell 2.8% after reporting its ninth straight quarter of falling revenue (http://www.marketwatch.com/story/exxon-mobil-profit-and-revenue-slide-again-2016-10-28-84853357).

Read:This market barometer says Trump still has a chance at the White House (http://www.marketwatch.com/story/this-market-barometer-says-trump-still-has-a-chance-at-the-white-house-2016-10-28)

Among other movers, Baker Hughes Inc.(BHI) rallied 7% after The Wall Street Journal reported that General Electric Co.(GE) is in talks to merge its oil-and-gas business with the oil-services company (http://www.marketwatch.com/story/general-electric-said-to-explore-baker-hughes-purchase-2016-10-27).

Hershey Co.(HSY) gained 7% after the chocolate company reported third-quarter earnings that beat estimates (http://www.marketwatch.com/story/hershey-third-quarter-earnings-beat-estimates-2016-10-28).

Amgen Inc.(AMGN) sank 10.2% after the biotechnology company late Thursday beat third-quarter earnings expectations and raised its profit outlook, but kept its sales outlook virtually unchanged (http://www.marketwatch.com/story/amgen-beats-profit-expectations-and-raises-its-outlook-2016-10-27).

U.S.-listed shares of Sanofi SA(SAN.FR) (SAN.FR) jumped 4.7% after the French drug giant lifted its profit outlook (http://www.marketwatch.com/story/sanofi-raises-profit-outlook-after-upbeat-results-2016-10-28).

See:

Other markets: Asia markets closed mostly lower (http://www.marketwatch.com/story/most-asian-markets-down-but-nikkei-trades-up-2016-10-27), but with Japan's Nikkei 225 bucking the trend. The Japanese index ended 0.6% higher as the yen weakened after data showed consumer prices dropped in September.

The ICE dollar index fell 0.6%.

Markets in Europe traded firmly lower (http://www.marketwatch.com/story/european-stocks-drop-as-anheuser-busch-cuts-view-french-data-disappoint-2016-10-28) and heading toward weekly losses.

Oil prices slumped (http://www.marketwatch.com/story/oil-prices-hold-steady-ahead-of-weekend-opec-meeting-2016-10-28) 1.5%, while metals where mixed (http://www.marketwatch.com/story/gold-futures-drift-lower-ahead-of-us-gdp-reading-2016-10-28).

(END) Dow Jones Newswires

October 28, 2016 14:07 ET (18:07 GMT)