Shares of technology companies fell as a rotation out of the sector continued.

The technology sector of the Standard & Poor's 500 rallied out of correction territory on Wednesday, only to slide back into the zone -- more than 10% from its Sept. 2 peak -- on Thursday and Friday.

"The late sell-off in tech stocks on Thursday came just as the sector appeared to be finding its feet again and served as a warning that one week of sharp declines doesn't necessarily mean the correction is complete," said Craig Erlam, senior market analyst at foreign-exchange brokerage OANDA Group, in a note to clients.

Shares of Facebook, Amazon.com, Apple, Microsoft, Netflix and Google parent Alphabet defied financial gravity for months, rising at eye-popping rates.

Investors in the "mega cap" companies have seen a sharp correction in recent weeks, and jittery price action Friday suggests anxiety that momentum could work against the companies on the way down.

Electric-truck startup Nikola shares fell again Friday, even as the company denied allegations of fraud outlined in a report published this week by short seller Hindenburg Research. Nikola had been flying high after a report that General Motors agreed to take a stake in the company.

Oracle shares gave back early gains despite a report of stronger-than-anticipated earnings from the business software maker.

Chewy shares fell sharply as the online pet-supply retailer's second-quarter sales growth was not quite as robust as investors had anticipated.

Like video-conferencing concern Zoom Video Communications and productivity software Slack Technologies, Chewy's business was thought to have been tailored toward "stay-at-home" lifestyle trends. Shares of all three have fallen sharply in early September.

Write to Rob Curran at rob.curran@dowjones.com