  GRB 100418A is a long burst at z=0.624 without detection of any associated
supernova (SN). Its lightcurves in both the prompt and afterglow phases are
similar to GRB 060614, a nearby long GRB without an associated SN. We analyze
the observational data of this event and discuss the possible origins of its
multi-wavelength emission. We show that its joint lightcurve at 1 keV derived
from Swift BAT and XRT observations is composed of two distinguished
components. The first component, whose spectrum is extremely soft (\Gamma =
4.32), ends with a steep decay segment, indicating the internal origin of this
component. The second component is a slowly-rising, broad bump which peaks at
~10^5 seconds post the BAT trigger. Assuming that the late bump is due to onset
of the afterglow, we derive the initial Lorentz factor (Gamma_0) of the GRB
fireball and find that it significantly deviates from the relation between the
Gamma_0 and Eiso of typical GRBs. We also check whether it follows the same
anti-correlation between X-ray luminosity and the break time observed in the
shallow decay phase of many typical GRBs, which is usually regarded as a signal
of late energy injection from the GRB central engine. However, we find that it
does not obey this correlation. We propose that the late bump could be
contributed by a two-component jet. We fit the second component with an
off-axis jet model for a constant medium density and find the late bump can be
represented by the model. The derived jet half-opening angle is 0.30 rad and
the viewing angle is 0.315 rad. The medium density is 0.05 cm^-3, possibly
suggesting that it may be from a merger of compact stars. The similarity
between GRBs 060614 and 100418A may indicate that the two GRBs are from the
same population and the late bump observed in the two GRBs may be a signal of a
two-component jet powered by the GRB central engine.
