The NYSE "has temporarily suspended trading in all symbols," the stock market said in a brief note.
"Additional information will follow as soon as possible."
All open orders will be cancelled if and when the exchange reopens, the NYSE said.
Earlier in the day, the exchange said it had a technical glitch that resulted in some traders not receiving confirmation of orders they had made or received for at least 221 different stocks.
Trading was then halted in all shares as of 11:32 a.m. ET.
The TSX was down 206 points at midday and appeared to be trading normally.
Before trading was halted, U.S. indexes were lower, as investors digested bleak economic news out of Greece and a Chinese stock market tumble that Beijing officials seem powerless to slow.
The Dow Jones industrial average was down 215 points, or 1.2 per cent, to 17,561.
The Standard & Poor's 500 gave up 24 points, or 1.2 per cent, to 2,057. The Nasdaq was down 73 points, or 1.5 per cent, to 4,924.