According to the NYSE's website, the major stocks impacted included Morgan Stanley, Verizon, AT&T, Nike, and McDonald's. Many stocks were shown to have abnormally large moves when the market opened, which may have triggered volatility halts.
CNBC's Bob Pisani said on "Squawk on the Street" that the issue appears to be technical and not something that happened on the trading floor.
Many of the companies impacted resumed trading before 9:45 a.m. ET. The NYSE said at roughly 9:50 a.m. that all of its systems were operational.