  Volume fluctuations are introduced in a statistical modelling of relativistic
particle collisions. The micro-canonical ensemble is used, and the volume
fluctuations are assumed to have the specific scaling properties. This leads to
the KNO scaling of the particle multiplicity distributions as measured in p+p
interactions. A striking prediction of the model is a power law form of the
single particle momentum spectrum at high momenta. Moreover, the mean
multiplicity of heavy particles also decreases as a function of the particle
mass according to a power law. Finally, it is shown that the dependence of the
momentum spectrum on the particle mass and momentum reduces to the dependence
on the particle energy. These results resemble the properties of particle
production in collisions of high energy particles.
