The New York Stock Exchange (NYSE) has suspended all trading after it experienced some unspecified technical issues.
At around 11.30am New York time, the NYSE said: "NYSE/NYSE MKT has temporarily suspended trading in all symbols. All open orders will be cancelled."
It later tweeted they were working to resolve the problem, adding this was not the result of a cyberattack.
The so-called Big Board added its NYSE Arca and NYSE Amex/Arca Options exchanges were not affected and were fully functioning.
US officials confirmed to CNBC there was no indication the NYSE was targeted by hackers.
About an hour before the first communication was made, it reported some prior technical issues had been resolved and all systems were functioning normally with a few exceptions.
Separately, the New York-based Nasdaq exchange said it was operating without any problems.
Earlier on 8 July, a computer system glitch forced United Airlines to ground all its flights in the US, a coincidence quickly brought up online, as the Wall Street Journal was also experiencing some issues.
NYSE said customers with questions should contact its trading services desk on 1-212-896-2830.