The New York Stock Exchange is canceling trades at six companies after 140 stock prices pitched up and down by more than 30-percent in a short period.
The stock swings that happened just after the morning bell and lasted till about 10:15 a.m.
The glitch affected various company stocks, from aluminum maker Alcoa to telecom giant AT&T.
The NYSE has canceled the trading of six stocks that include Wizzard Software and Quicksilver Resources.
Some trading blogs place the blame on a technical problem at trade processing firm Knight Capital Group. In a statement, the company admits it had a technical issue "related to the routing of shares of approximately 150 stocks to the NYSE."
The NYSE says systems and circuit breakers operated normally during the snafu. Regulators order that trading be halted after stocks swing outside of 10-percent in either direction.