In the last trading session, the U.S. stocks fell, erasing all of the gains it made in the previous session. In fact, Dow Jones again slipped into a negative territory for 2015. Among the top ETFs, investors saw (SPY – ETF report) lose 1.0%, (DIA – ETF report) shed 0.8% and (QQQ – ETF report) move lower by 0.6% on the day.

Two more specialized ETFs are worth noting as both saw trading volume that was far outside of normal. In fact, both these funds experienced volume levels that were more than double their average for the most recent trading session. This could make these ETFs ones to watch out for in the days ahead to see if this trend of extra-interest continues:

(PXE – ETF report): Volume 4.55 times average

This energy ETF was in focus yesterday as around 147,000 shares moved hands compared with an average of roughly 34,000 shares a day. We also saw some price movement as PXE lost nearly 4% in the last session.

The movement can largely be blamed on sliding oil price, which was below $40 once again, and can have a big impact on energy stocks like what we find in this ETF portfolio. PXE was down 2% over the past one-month and currently has a Zacks ETF Rank of 4 or ‘Sell’ rating with a High risk outlook.

(FXU – ETF report): Volume 4.48 times average

This utility ETF was under the microscope yesterday as about 668,000 shares moved hands. This compares with an average trading day of around 151,000 shares and came as FXU shed 2.6% in the session.

The big move was largely the result of the prospect of a rates hike later this month that has dampened the appeal for the income generating securities. FXU was down 5% in the past one month and currently has a Zacks ETF Rank of 3 or ‘Hold’ rating with a Medium risk outlook.