  Long duration gamma-ray bursts are commonly associated with the deaths of
massive stars. Spectroscopic studies using the afterglow as a light source
provide a unique opportunity to unveil the medium surrounding it, probing the
densest region of their galaxies. This material is usually in a low ionisation
state and at large distances from the burst site, hence representing the normal
interstellar medium in the galaxy. Here we present the case of GRB 090426 at
z=2.609, whose optical spectrum indicates an almost fully ionised medium
together with a low column density of neutral hydrogen. For the first time, we
also observe variations in the Ly alpha absorption line. Photoionisation
modeling shows that we are probing material from the vicinity of the burst (~80
pc). The host galaxy is a complex of two luminous interacting galaxies, which
might suggest that this burst could have occurred in an isolated star-forming
region outside its host galaxy created in the interaction of the two galaxies.
