  The angular power spectrum of the cosmic microwave background (CMB)
temperature anisotropies is a good probe to look into the primordial density
fluctuations at large scales in the universe. Here we re-examine the angular
power spectrum of the Wilkinson Microwave Anisotropy Probe data, paying
particular attention to the fine structures (oscillations) at $\ell=100 \sim
150$ reported by several authors. Using Monte-Carlo simulations, we confirm
that the gap from the simple power law spectrum is a rare event, about
2.5--3$\sigma$, if these fine structures are generated by experimental noise
and the cosmic variance. Next, in order to investigate the origin of the
structures, we examine frequency and direction dependencies of the fine
structures by dividing the observed QUV frequency maps into four sky regions.
We find that the structures around $\ell \sim 120$ do not have significant
dependences either on frequencies or directions. For the structure around $\ell
\sim 140$, however, we find that the characteristic signature found in the all
sky power spectrum is attributed to the anomaly only in the South East region.
