  We discuss some of the preliminary results and findings derived from the
analysis of a first sample of flares detected by the XRT on board Swift. The
analysis shows that the morphology of flares is the one we expect from the
collision of ultra-relativistic shells as it happens during the internal shock
model proposed by Rees and Meszaros in 1994. Furthermore the Delta(t)/t ratio
and the decay-time to rise-time ratio have mean values that are in good
agreement with the values observed in the prompt emission pulses that are
believed to originate from internal shocks. The conclusion is that the flare
analysis favors the internal shock as due to shells that have been ejected by
the central engine after the prompt emission. The central engine seems to
remain active and capable of generating large amounts of energy also at later
times. More data are needed to establish whether or not some of the flares
could be due to shells that have been emitted with small Lorentz factor at the
time of the prompt emission and generate later time flares due to the catch up
of these shells.
