  The successful operation of dedicated detectors has brought us valuable
information for understanding the central engine and the progenitor of
gamma-ray bursts (GRBs). For instance, the giant X-ray and optical bumps found
in some long-duration GRBs (e.g. GRBs 121027A and 111209A) imply that some
extended central engine activities, such as the late X-ray flares, are likely
due to the fall-back of progenitor envelope materials. Here we systemically
search for long GRBs that consist of a giant X-ray or optical bump from the
Swift GRB sample, and eventually we find 19 new possible candidates. The
fall-back accretion model could well interpret the X-ray and optical bump for
all candidates within a reasonable parameter space. Six candidates showing
simultaneous bump signatures in both X-ray and optical observations, which
could be well fitted at the same time when scaling down the X-ray flux into
optical by one order of magnitude, are consistent with the standard
$F_{\nu}\propto\nu^{1/3}$ synchrotron spectrum. The typical fall-back radius is
distributed around $10^{10}\rm-10^{12}$ cm, which is consistent with the
typical radius of a Wolf-Rayet star. The peak fall-back accretion rate is in
the range of $\sim 10^{-11}-10^{-4}M_{\odot} \ \text{s} ^{-1}$ at time
$\sim10^{2}- 10^{5}~\rm s$, which is relatively easy to fulfill as long as the
progenitor's metallicity is not too high. Combined with the sample we found,
future studies of the mass supply rate for the progenitors with different mass,
metallicity, and angular momentum distribution would help us to better
constrain the progenitor properties of long GRBs.
