Trading resumed on the New York Stock Exchange at 3:10 p.m. Eastern time after an outage of more than three hours caused by technical problems.
There was no interruption at the dozens of other U.S. stock exchanges Wednesday, including the Nasdaq, so investors were still able to buy and sell stocks easily.
The NYSE didn't say what the problem was but described it as internal issue and not the result of a breach of its systems. Trading was halted starting at 11:30 a.m.
"It's not a good day. I don't' feel good for our customers who are having to deal with the fallout," NYSE president Thomas Farley told CNBC.
Officials and the exchange have said that there is no indication that the problem is the result of a cyber-attack. Officials have also said there is no sign that it is related to a computer outage that grounded United Airlines flights Wednesday morning. The Wall Street Journal's website also experienced technical issues around noon.
The FBI told NBC 4 New York it reached out to the NYSE to offer its assistance but was told the glitch was technical.
The Dow Jones industrial average and other indexes were trading at about where they were before the NYSE technical problem occurred in the late morning. Major indexes continued to move as stocks were traded on other exchanges.
The halt in trading hasn't stopped trading of NYSE-listed shares, which continue to change hands on other exchanges.
Other exchanges compete for the orders made to buy and sell stocks.
Tom Caldwell, who runs an investment firm with stakes in several exchanges, says there are some 60 exchanges and trading venues that can take orders when one goes down, and so he isn't worried.
"It's disruptive, but not wildly disruptive," said Caldwell, chairman of Caldwell Securities. "You have so many competing exchanges."
--Jonathan Dienst contributed to this story.