Three major computer glitches in as many hours have hit the US, one of them shutting down the New York Stock Exchange.
The halt in trading at 11:30 local time has been described as unprecedented in its scale.
Earlier United Airlines temporarily grounded all of its flights due to a technical problem.
The Wall Street Journal website also crashed.
So far there is no indication of a link between the three incidents, but investigations are underway at each location.
President Obama has been briefed on the NYSE shutdown and the White House was due to make a statement.
The US Department of Homeland Security said there was no indication of anything “malicious” at the NYSE.
Homeland Security Secretary Jeh Johnson attempted to give reassurances about the glitches.
“I have spoken to the CEO of United, Jeff Smisek, myself,” he said. “It appears from what we know at this stage that the malfunctions at United and the stock exchange were not the result of any nefarious actor,”
The Nasdaq exchange was operating normally.
(1 of 2) We’re experiencing a technical issue that we’re working to resolve as quickly as possible.— NYSE (@NYSE) julio 8, 2015
We experienced a network connectivity issue. We are working to resolve and apologize for any inconvenience.— United (@united) julio 8, 2015