  We analyze the X-ray properties of a near-infrared selected (Ks < 20) sample
of spectroscopically identified Extremely Red Objects (R-Ks>5) in a region of
the Chandra Deep Field-South using the public 1 Ms observation. The 21 objects
were classified, on the basis of deep VLT spectra, in two categories: 13 dusty
star-forming galaxies showing [OII] emission, and 8 early-type galaxies with
absorption features in their optical spectra. Only one emission line object has
been individually detected; its very hard X-ray spectrum and the high intrinsic
X-ray luminosity unambiguously reveal the presence of an obscured AGN. Stacking
analysis of the remainder 12 emission line objects shows a significant
detection with an average luminosity L(X)~8x10^{40} erg/s in the rest-frame
2-10 keV band. The stacked counts of the 8 passive galaxies do not provide a
positive detection. We briefly discuss the implications of the present results
for the estimate of the Star Formation Rate (SFR) in emission line EROs.
