  Evidence for the central engine of gamma-ray bursts (GRBs) has been collected
in the Neil Gehrels \emph{Swift} data. For instance, some GRBs show an internal
X-ray plateau followed by very steep decay, which is difficult to be
interpreted within the framework of a black hole (BH) central engine, but are
consistent within a rapidly spinning magnetar engine picture. The very steep
decay at the end of the plateau suggests a sudden cessation of the central
engine, which is explained as the collapse of a supra-massive magnetar into a
black hole when it spins down. Here we propose that some additional evidence,
such as a second X-ray plateau feature would show up, if the fall-back
accretion could activate the newborn BH and sufficient energy could be
transferred from the newborn BH to the GRB blast wave. With a systematic data
analysis for all long GRBs, we find three candidates in \emph{Swift} sample,
i.e., GRBs 070802, 090111, and 120213A, whose X-ray afterglow light curves
contain two plateaus, with the first one being an internal plateau. We find
that in a fairly loose and reasonable parameter space, the second X-ray plateau
data for all 3 GRBs could be well interpreted with our proposed model. Future
observations are likely to discover more similar events, which could offer more
information of the properties of the magnetar as well as the newborn BH.
