  We investigate a particular regularization of big bang singularity, which
remains within the domain of 4-dimensional general relativity but allowing for
degenerate metrics. We study the geodesics and geodesic congruences in the
modified Friedmann-Lema\^itre-Robertson-Walker universe. In particular, we
calculate the expansion of timelike and null geodesic congruences. Based on
these results, we also briefly discuss the cosmological singularity theorems.
