The New York Stock Exchange on Wednesday morning abruptly halted all trading with little explanation. Trading resumed about three and half hours later.
"NYSE/NYSE MKT has temporarily suspended trading in all symbols," the exchange said in a statement on its market status page, referring to the terse letter combinations that represent companies like Hewlett-Packard (HPQ), Twitter (TWTR) and Verizon Communications (VZ). "Additional information will follow as soon as possible."
All open orders were cancelled. But during the downtime, trading in NYSE-listed stocks occurred on other exchanges, including the Nasdaq.
On its Twitter feed, the NYSE attributed the halt, which began at 11:32 a.m. Eastern, to an internal technical issue -- not a cyber breach -- and said it was working to resolve the issue "as quickly as possible."
Trading resumed at about 3:10 p.m. Eastern. But the exchange has yet to offer any further details about what caused the problem.
(1 of 3) The issue we are experiencing is an internal technical issue and is not the result of a cyber breach.— NYSE (@NYSE) July 8, 2015
Even without the NYSE glitch, investors were already nervous over global concerns like the debt crisis in Greece and a meltdown in Chinese stocks.
It wasn't a good day for technology in general. Earlier Wednesday, United Airlines grounded its flights due to a technical matter as well, but that has since been resolved. And The Wall Street Journal's home page also went down for a brief period following the NYSE halt.
Outages like this are very rare for US markets. The last one, also blamed on a technical glitch, wasin August 2013.
Update 12:32 p.m. PT: Added that NYSE trading has resumed.