Production of double strange Xi- hyperons at sub-threshold energies has been observed by HADES experiment [1] to be unexpectedly enhanced in comparison to theoretical estimates. We suggest, that K0* <--> anti-K0* oscillation of neutral kaons can be affected in very dense baryonic matter in a specific way, which may result in the oscillation length 5-10 fm. This allows for the strangeness violation process (s'd) --> (sd') to occur in a very short time, within the volume of dense hadronic medium, and excessive double-strange hyperons can be created via rescattering anti-K0* + (Sigma , Lambda) --> Xi + pi interactions. The significance of such processes is underestimated, if global strangeness conservation is assumed in p + A and A + A collisions at low energies.