Nasdaq trading halted by glitch for 3 hours
The Nasdaq exchange has resumed trading, after an earlier suspension for a "technical issue".
Trading had been halted for around three hours, with the US exchange citing a problem distributing stock price quotes.
After resuming trading at 15:25 EST (20:25 GMT), the Nasdaq closed up 1% to 3,102. Trading had been halted at 12:14 EST.
Trading on the other US exchanges was uninterrupted.
The Nasdaq is the second-largest stock exchange in the US, and the world's largest electronic stock market. It is dominated by major tech stocks such as Apple and Facebook.
Nasdaq said that trades executed between 12:14:03 and 12:23:31 would stand.
But trades between 12:23:31 and the resumption of trading would not stand, it said.
The US Securities and Exchange Commission said it wants to meet with Nasdaq following the outage.
"Today's interruption in trading, while resolved before the end of the day, was nonetheless serious and should reinforce our collective commitment to addressing technological vulnerabilities of exchanges and other market participants," SEC chairwoman Mary Jo White said.
Shares in the stock exchange's owner Nasdaq OMX Group - which themselves trade on the Nasdaq - fell over 3% by the end of the day.
This is not the first technical glitch to affect recent US share trading.
Last year, trading was delayed in the much-anticipated debut of social network Facebook.
Nasdaq agreed to pay a $10m penalty to settle federal civil charges after regulators said its systems and decisions disrupted the float, and it paid out a further $62m in reimbursements to investment firms that lost money because of the problems.
Its rival, the New York Stock Exchange, had similar problems last year when a software glitch at market-maker Knight Capital caused huge price swings in trading in 140 stocks. During Thursday's suspension, Nasdaq advised firms to route their trades elsewhere.