A single trade in Apple Inc shares far below where the stock had previously been priced on Wednesday was canceled, said a spokesperson at the exchange where it was generated.
One trade of 100 shares was executed at $321.87, more than 7.5 percent below Tuesday's close, before being busted by the BATS exchange.
The trade was busted under BATS clearly erroneous trade policy, a spokesperson for the exchange said in an email.
Apple shares closed up 0.4 percent for the day at $349.57.
Unusual activity in Apple also occurred on February 10 when its shares dropped by more than 2 percent in just minutes before recovering, another example of unexplained stock volatility that has caused headaches for regulators and investors.
The latest sign of abrupt volatility comes almost a year after the May 6, 2010, flash crash, which wiped out nearly $1 trillion in market capitalization from the U.S. stock market in a few minutes.
Apple said it does not comment on stock moves.
(Reporting by Rodrigo Campos; additional reporting by Chuck Mikolajczak; Editing by Dan Grebler)