The iShares U.S. Utilities ETF (IDU) is seeing unusually high volume in afternoon trading Monday, with over 7.3 million shares traded versus three month average volume of about 548,000. Shares of IDU were down about 1.8% on the day.

Components of that ETF with the highest volume on Monday were AES (AES), trading down about 1.9% with over 5.4 million shares changing hands so far this session, and Southern (SO), off about 1.7% on volume of over 4.1 million shares. UIL Holdings (UIL) is the component faring the best Monday, up by about 0.5% on the day, while Dynegy (DYN) is lagging other components of the iShares U.S. Utilities ETF, trading lower by about 3.7%.