  Aims: We test the technique of spectro-astrometry as a potential method to
investigate the close environment of massive young stars.
  Method: Archival VLT near infrared K band spectra (R=8900) of three massive
young stellar objects and one Wolf-Rayet star are examined for
spectro-astrometric signatures. The young stellar objects display emission
lines such as Brackett gamma, CO 2-0 and CO 3-1 that are characteristic of
ionised regions and molecular disks respectively. Two of the sample sources
also display emission lines such as NIII and MgII that are characteristic of
high temperatures.
  Results: Most of the emission lines show spectro-astrometric signal at
various levels resulting in different positional displacements. The shapes and
magnitudes of the positional displacements imply the presence of large
disk/envelopes in emission and expanding shells of ionised gas. The results
obtained for the source 18006-2422nr766 in particular provide larger estimates
(> 300AU) on CO emitting regions indicating that in MYSOs CO may arise from
inner regions of extended dense envelopes as well.
  Conclusions: The overall results from this study demonstrate the utility of
spectro-astrometry as a potential method to constrain the sizes of various
physical entities such as disks/envelopes, UCHII regions and/or ionised shells
in the close environment of a massive young star.
