  The DELPHI detector at LEP has been used to measure multi-muon bundles
originating from cosmic ray interactions with air. The cosmic events were
recorded in ``parasitic mode'' between individual e+e- interactions and the
total live time of this data taking is equivalent to 1.6x10^6 seconds. The
DELPHI apparatus is located about 100 metres underground and the 84 metres rock
overburden imposes a cut-off of about 52 GeV/c on muon momenta. The data from
the large volume Hadron Calorimeter allowed the muon multiplicity of 54201
events to be reconstructed. The resulting muon multiplicity distribution is
compared with the prediction of the Monte Carlo simulation based on
CORSIKA/QGSJET01. The model fails to describe the abundance of high
multiplicity events. The impact of QGSJET internal parameters on the results is
also studied.
