  HESS J1626-490, so far only detected with the H.E.S.S. array of imaging
atmospheric Cherenkov telescopes, could not be unambiguously identified with
any source seen at lower energies.
  Therefore, we analyzed data from an archival XMM-Newton observation, pointed
towards HESS J1626-490, to classify detected point-like and extended X-ray
sources according to their spectral properties. None of the detected X-ray
point sources fulfills the energetic requirements to be considered as the
synchrotron radiation (SR) counterpart to the VHE source assuming an Inverse
Compton (IC) emission scenario. Furthermore, we did not detect any diffuse
X-ray excess emission originating from the region around HESS J1626-490 above
the Galactic Background. The derived upper limit for the total X-ray flux
disfavors a purely leptonic emission scenario for HESS J1626-490.
  To characterize the Interstellar Medium surrounding HESS J1626-490 we
analyzed ^{12}CO(J=1-0) molecular line data from the Nanten Galactic plane
survey and HI data from the Southern Galactic Plane Survey (SGPS). We found a
good morphological match between molecular and atomic gas in the -27 km/s to
-18 km/s line-of-sight velocity range and HESS J1626-490. The cloud has a mass
of 1.8x10^4 M_sun and is located at a mean kinematic distance of d = 1.8 kpc.
Furthermore, we found a density depression in the HI gas at a similar distance
which is spatially consistent with the SNR G335.2+00.1.
  Therefore, the most likely origin of the VHE gamma-ray emission observed with
H.E.S.S. is the hadronic interaction of cosmic rays with a moderately dense
molecular cloud, which we detected with Nanten. The application of a detailed
hadronic model for cosmic ray transport and interaction shows that the cosmic
rays could originate from the nearby SNR G335.2+00.1.
