An error in trading at Barclays is being blamed for some unusual swings in stocks this week, reports Bloomberg News. The stocks affected included AOL, Nabors, Nasdaq OMX, and Caterpillar Inc, along with dozens of others.

The price swings came about because the trading orders were entered incorrectly, "causing the transactions to be executed immediately." The error caused "split-second swings," with AOL experiencing the biggest swing, declining 11 percent. The dip took only a second to correct, but some AOL transactions did have to be canceled. Other transactions which should have processed were canceled. 

Bloomberg heard through an insider source that Barclays clients were not affected by the snag. The issue put less than $4 million at stake in just a matter of seconds, though an exact number could not be confirmed. Barclays has not made a public comment on the matter.