  We study the power asymmetry between even and odd multipoles in the
multipolar expansion of CMB temperature data from WMAP, recently reported in
the literature. We introduce an alternate statistic which probes this effect
more sensitively. We find that the data is highly anomalous and consistently
outside $2\sigma$ significance level in the whole multipole range $l=[2,101]$.
We examine the possibility that this asymmetry may be caused by the foreground
cleaning procedure or by residual foregrounds. By direct simulations, using the
Planck Sky Model for foregrounds we rule out this possibility. We also examine
several possible sub-dominant foregrounds, which might lead to such an
asymmetry. However in all cases we are unable to explain the signal seen in
data. We next examine cleaned maps, using procedures other than the one
followed by the WMAP Science team. Specifically we analysed the maps cleaned by
the IPSE procedure, Needlets and the harmonic ILC procedure. In all these cases
we do not find a statistically significant signal of power asymmetry. This is
in contrast to the result obtained by the WMAP best fit power spectrum as well
as the ILC map. Finally, we test for the contribution of low-$l$ multipoles to
the observed power asymmetry. We find that if we eliminate the first six
multipoles, $l=[2,7]$, the significance falls below $2\sigma$ CL. Hence we find
that the signal gets dominant contribution from low-$l$ modes.
