After-hours buzz: Alphabet, Under Armour, Southwestern Energy & more

Wall Street, after hours
Curtis Means | NBC NewsWire | Getty Images

Check out the companies making headlines after the bell Tuesday:

Alphabet's shares sank briefly in light trading after hours, as the company announced a partnership to build self-driving cars with Fiat Chrysler. The deal will focus on self-driving minivans to be used as test vehicles.

Shares of Under Armour fell in extended trading after the company named a new chief merchandising officer. The athletic wear brand said that Kip Fulks would serve as interim chief merchandising officer as Henry Stafford steps down in July. Michael Lee, co-founder of MyFitnessPal, will also serve as Under Armour's chief digital officer starting in July, replacing Robin Thurston, the company said. There was no reason given for the C-suite shake-up.

Shares of energy companies were higher after the American Petroleum Institute reported a lower-than-expected rise in U.S. crude oil stockpiles. Crude inventories rose by 1.3 million barrels in the week of April 29 to 539.7 million, short of analysts' expectations for an increase of 1.7 million barrels, according to Reuters.

Southwestern Energy, Newfield Exploration, Devon Energy, EOG Resources and Cabot Oil and Gas all bounced after hours. Many of the companies focus on natural gas, an industry that was praised by vocal hedge fund manager David Einhorn earlier in the week.

CBS shares rose after the media company reported better-than-expected earnings. CBS posted earnings of $1.02 per share on revenues of $3.85 billion, higher than the 94 cents per share on $3.83 billion expected by Wall Street, according to Thomson Reuters consensus estimates. The quarterly results were "just the beginning" as the company plans a new revenue streams for the next five years, said CEO Leslie Moonves, in an earnings call.

Biotechnology firm Illumina saw its shares tumble after earnings missed analyst estimates. The company, which makes gene sequencing technology, posted adjusted first-quarter earnings of 71 cents per share, below the 74 cents expected by Wall Street, according to the Associated Press.

"As we have previously shared, Q1 was a slower start to the year than we expected," CEO Jay Flatley said, in a statement. "Our view of the growth potential of the sequencing market remains unchanged, as the largest opportunities are in their earliest stages of development. In the near-term, we are focused on improving execution to restore the growth rate we believe our markets can support."

— Reuters, the AP and CNBC's Alex Crippen and Julia Boorstin contributed to this report.