NYSE Resumes Trading After Glitch

Technical issues had forced exchange to halt trading.

The New York Stock Exchange resumed trading after technical problems forced a nearly four-hour halt on Wednesday, jarring investors and traders already unnerved by recent volatility across global financial markets.

NYSE was quick to dismiss speculation that the trading disruption was caused by hacking. On Twitter, the exchange said the problem “is not the result of a cyber breach.”

The shutdown was isolated to specific trading venues, and investors could still buy and sell NYSE-listed stocks on other venues, such as NYSE’s own Arca exchange. NYSE is owned by Intercontinental Exchange Inc.

The suspension came in the middle of a broad selloff in U.S. stocks that was spurred by a deepening rout in China’s stock markets. It came on a day when the Federal Reserve disclosed minutes from its last meeting, a release that in the past has prompted swings in stocks. The glitch is also the latest incident illustrating the fragility of trading systems that allow capital markets to function.

NYSE told floor traders that the problem originated in a software update it installed last night, according to Peter Costa, a floor trader and president of Empire Executions. “They told us they did some software updates overnight and tested it without problems, but this morning something happened,” Mr. Costa said.

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