  As a complement to our optical and near-infrared study of the continuum
properties of GX 339-4 in the two hard and one soft state observations made by
the ESO/VLT FORS2 and ISAAC in early 2010, we report here on the results of our
spectral line analysis for the same observations. In the soft state, the
presence of strong Balmer, Paschen and Brackett emission lines points to the
optical and near-infrared spectra stemming from the irradiated chromosphere of
the optically thick and geometrically thin accretion disc. Most of these HI
features are still detected in emission in both hard states but are veiled by
the compact jets continuum. We also confirm the presence of a broad Hbeta
absorption feature, prominent in the soft state and shallower in the first hard
state, which we argue forms in the deep layers of the optically thick accretion
disc. However, this trough is absent in the second hard state, a likely
consequence of the formation of a geometrically thick extended envelope that
arises above the disc plane and eventually enshrouds the region where the Hbeta
absorption feature forms. We detect this envelope through the presence of a
broad Pabeta emission line, which is constant during the first hard state but
correlates with the underlying continuum during the second hard state, pointing
to changing physical properties. We consider that this behaviour may be
consistent with the launch of a thermally-driven accretion disc wind during the
second hard state.
