Sudden 9% drop in Apple stock triggers temporary trading halt [u]

Update: The culprit of the AAPL stock price drop has been linked to volatility caused by three erroneous trades from BATS' systems. BATS Global Markets Chief Executive Joe Ratterman announced that he was withdrawing his company's IPO after Friday's fiasco. The original price for the 6.3 million share IPO was set between $16 and $18 a share, but the stock ended the day down 99.76 percent to finish at $0.04. Apple shares leveled out and finished the trading day at $596.05, down 0.55 percent.

Just before 11 a.m., AAPL plunged to $542.80, down more than 9 percent in what The Wall Street Journal said was likely an accidental "fat-finger trade." Five minutes later, trading resumed at a price just under $600.

The temporary halt was triggered by orders placed through the BATS Global Markets, which were well below where Apple had previously been trading. Orders first came in at $551.66 and quickly dropped to $542.80.

BATS has been facing technical issues, as its website notes it is "actively investigating an issue." Issues in the exchange have apparently applied to symbols ranging from 'A' to 'BF.'

BATS relies on high-speed traders as its key clients, catering to trading firms that capitalize on nanosecond price changes. Coincidentally, on Friday the Journal revealed that the SEC has initiated a probe into rapid-fire trade firms, prompted by the "flash crash" of May 2010 when stocks fell and rebounded sharply within minutes.