Nasdaq Inc said it cancelled trades that spanned a two-minute period before the opening bell on Wednesday which affected about 50 securities.

The exchange initially said it was investigating "potentially erroneous transactions" that occurred between 9:23 a.m. ET (1323 GMT) and 9:25 a.m. ET (1325 GMT) and included names such as Michaels Companies, Mercury General Corp and Mohawk Industries.

Within the hour, Nasdaq announced that it had determined to cancel all of the trades within the timeframe that were executed at 30% above or below the consolidated closing price.