Trading was halted on the New York Stock Exchange about 3.5 hours Wednesday because of what the market called "a technical issue" -- the longest suspension in recent years at the exchange.
The halt began about 11:32 a.m. and ended after 3 p.m. Market officials said all open orders were canceled.
The NYSE said the trading suspension was "not the result of a cyberbreach," and that it halted trading itself "to avoid problems arising from our technical issue."
NYSE stocks continued to trade on other exchanges, including the Nasdaq Market. The NYSE is one of 11 exchanges and more than 50 private venues where American stocks change hands. The NYSE, once the dominant domestic stock exchange, accounted for only about 12.5 percent of U.S. stock market volume since the beginning of July, according to data from BATS Global Markets, an exchange operator based in Lenexa, Kansas.
In fact, the outage didn't reduce the trading volume of major Long Island companies. Seven of the region's 10 top public companies by revenue posted higher trading volume Wednesday than usual, according to Google Finance.
"What this glitch really proves -- and this is sad news for the exchange -- is that we can live without the New York Stock Exchange," said Mitchell O. Goldberg, president of ClientFirst Strategy Inc., an investment firm in Dix Hills. "Trading has been decentralized thanks to network computers."
The continued trading "speaks to the strength and resilience of our financial markets," said Ken Dreifus, deputy chairman of the undergraduate business department at Touro College, in Manhattan.
Still, the shutdown came at a time of investor insecurity over such issues as Greece's struggle to avoid economic collapse, plunging stock prices in China, and Puerto Rico's declaration that it couldn't continue making payments on its bonds.
The Dow Jones industrial average closed down 261 points, or 1.5 percent, to 17,515.42.
The S&P 500 gave up 35 points, or 1.7 percent, to close at 2,046.88. The Nasdaq was down 88 points, or 1.8 percent, at 4,909.76.
Craig Ferrantino, president of Craig James Financial Services, a Melville investment and financial planning firm, said he had about a dozen calls, emails and texts from clients concerned about the shutdown. "The NYSE shutdown adds to the fear that things are spinning out of control globally," he said.
The NYSE didn't go into detail about the nature of its "technical issue."
Top U.S. law enforcement and security officials said they didn't see a link between the outage at the NYSE, the temporary grounding of United Continental flights and a temporary malfunction of The Wall Street Journal's website, which also occurred Wednesday.
"We do not see any indication of a cyberbreach or a cyber-attack," FBI director James Comey told the Senate Intelligence committee.
The outage prompted comparisons to a 2013 "flash freeze" when a software glitch halted trading on the Nasdaq Market for three hours.
"It is the most significant outage since Nasdaq's blackout," Eric Scott Hunsader, CEO of Nanex, a data-feed company, told CNN.
Not all investors were worried. At the Commack office of the investment firm Edward Jones, financial adviser Shelly M. Newman reported receiving only one call from an out-of-state client. "You can buy any stock you want today," she said. "Our trades are going through as normal."
With AP and Bloomberg News