NEW YORK — Computer breakdowns shook American equity trading for the second time this week, freezing thousands of stocks listed on the Nasdaq Stock Market for three hours and raising fresh concerns about the fragility of exchanges.
The second-biggest American exchange operator, home to 3,200 companies from 37 countries, halted transactions in all of its securities shortly after noon Thursday, a decision that caused buying and selling to stop on its platform and dozens of others where the securities trade. Errors in the feed used to disseminate quotes and prices were to blame, Nasdaq said on its website.
Many of the country’s most-traded shares, from Apple to Intel and Facebook, ground to a virtual standstill as brokers were unable to execute customer orders. The Nasdaq 100 equity index didn’t update during the outage and volume in stocks listed on the rival New York Stock Exchange also dwindled as liquidity dried up around the country.
“The real fear is that we get stuck wearing some kind of risk because of an interruption that is not of our doing,” said Max Breier, a senior equity derivatives trader at BMO Capital Markets Corp. in New York. “Any halt in information or ability to trade is going to hinder our ability to manage our risk and take positions.”
President Barack Obama was briefed on the disruption in the afternoon by his chief of staff, Denis McDonough, Josh Earnest, deputy White House press secretary, said in an email to reporters traveling with the president in upstate New York. The Securities and Exchange Commission was also monitoring the situation.
Shares covered by the halt began to change hands again at about 3:25 p.m. in New York.
The disruption, just two days after options markets were roiled by mistaken trades sent by Goldman Sachs, is the latest in a series of computer malfunctions that have raised questions about the reliability of electronic markets.
Nasdaq faced criticism last year when its computers mishandled the public debut of Facebook, causing hundreds of millions of dollars in losses for its member firms.
Though the cause was unclear, the outage is more bad news for Robert Greifeld, the Nasdaq chief executive officer whose reputation suffered in the Facebook IPO. Company representatives didn’t respond to emails and phone calls asking what triggered the breakdown.
“This is just another one of those headaches that are going on with this electronic stuff,” Frank Ingarra, head trader at Greenwich, Conne.-based NorthCoast Asset Management LLC, said in a phone interview.
Nasdaq’s own shares, which were covered by the halt, fell 3.9 percent to $30.32 as of 3:50 p.m. in New York.
Trading failures are multiplying as global financial markets get more complex. U.S. equity trading, which began one group of men under a buttonwood tree on Wall Street more than two centuries ago, has become dispersed among more than 50 computerized platforms accessible around the world.
“A trading halt is pretty big on a major public market,” said Douglas Cote, chief market strategist at ING U.S. Investment Management in New York. His firm oversees $190 billion. “It’s kind of like being in an airplane. It’s risky. Even though planes have had some problems, you don’t not fly because of it.”