A growing number of long Gamma-Ray Bursts are indisputably associated with
core-collapse supernovae, discovered through optical spectroscopy and/or photometry
of the GRB afterglow. Three such bursts show evidence of a thermal component in the
early X-ray afterglow emission, claimed by some to be a signature of supernova shock
breakout. This component could equally be attributed to central engine activity. We
examine the X-ray afterglows of all Swift GRBs with associated optical supernovae in
search of a thermal X-ray component, comparing these results to those of
non-SN-associated GRBs to add to the debate on the origin of this emission.