  The X-ray plateau followed by a steep decay ("internal plateau") has been
observed in both long and short gamma-ray burst (GRBs), implying a millisecond
magnetar operating in some GRBs. The sharp decay at the end of plateau, marking
the abrupt cessation of the magnetar central engine, has been considered as the
collapse of a supra-massive magnetar to a black hole (BH) when it spins down.
If "internal plateau" is indeed the evidence of a magnetar central engine, a
natural expectation is a signature from the new-born BH in some candidates. In
this work, we find that GRB 070110 is a particular case, which shows a small
X-ray bump following its "internal plateau". We interpret the plateau with a
spin-down supra-massive magnetar and the X-ray bump with a fall-back BH
accretion. This indicates that the new-born BH is likely active in some GRBs.
Therefore, GRB 070110-like events may provide a further support to the magnetar
central engine model and enable us to investigate the properties of the
magnetar as well as the new-born BH.
