Apple Stock Trading Halted Briefly on Sudden 9% Drop

BusinessInsider reports some strange activity on Apple's stock today. Trading was halted due to an abrupt drop of over 9%.

The stock crashed 9% to $542.80 before trading was stopped. When the stock started trading again, it opened at $598.39

Trading has since resumed, but there has been no clarification on what happened. StreetInsider speculates that it was "an apparent errant trade".

Image of drop from WSJ

Update: Bloomberg pinpoints the issue to a single trade for 100 shares executed by Bats Global Markets Inc.

A single trade for 100 shares executed on a Bats venue briefly sent Apple, the world’s most valuable company, down to $542.80, triggering a circuit breaker that paused the shares. The order was executed at 10:57 a.m. New York time. Two more transactions, which sent the stock back above $598, were made before the halt. The stock stayed around that level once trading resumed.