  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
X-ray point-sources according to their spectral properties and their
near-infrared counterparts from the 2MASS catalog. Furthermore, we
characterized in detail the diffuse X-ray emission from a region compatible
with the extended VHE signal. 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, HI data from the Southern Galactic Plane
Survey and Spitzer data from the GLIMPSE and MIPSGAL surveys. 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. We did not detect any
diffuse X-ray excess emission originating from the region around HESS J1626-490
above the Galactic Background and the derived upper limit for the total X-ray
flux disfavors a purely leptonic emission scenario for HESS J1626-490. We found
a good morphological match between molecular and atomic gas in the -27km/s to
-18km/s line-of-sight velocity range and HESS J1626-490. The cloud has a mass
of 1.8$times 10^4$M$_{odot}$ 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. We
discuss various scenarios for the VHE emission, including the CO molecular
cloud being a passive target for cosmic ray protons accelerated by the nearby
SNR G335.2+00.1.
