We have investigated 631 time profiles of gamma ray bursts from the BATSE
database searching for observable signatures produced by microlensing events
related to natural wormholes. The results of this first search of topologically
nontrivial objects in the Universe can be used to constrain their number and
mass.Comment: Mod. Phys. Lett. A. (in press) Latex (revtex style) with no figure