We present here a study of XMM-Newton data of two distant galaxy cluster candidates .
One of these was discovered serendipitously in near infrared data , CL~J0533-2411 , the other one corresponds to the cluster EIS~J0533-2412 part of the EIS cluster survey .
The estimated redshift of CLÂ J0533-2411 is z = 1.2 - 1.7 .
EISÂ J0533-2412 is a rich system ( \Lambda _ { cl } = 299 ) , with a spectroscopically confirmed redshift of z = 1.3 .
Both galaxy concentrations show firm X-ray detections , located within 30 ^ { \prime \prime } of their optical center .
However , we can not resolve the sources with XMM-Newton .
If the X-ray emission originates from the X-ray emitting intra-cluster medium ( ICM ) it would be extremely concentrated which is rather unlikely ( core radii below 14 ~ { } { h _ { 65 } ^ { -1 } ~ { } kpc } and 40 ~ { } { h _ { 65 } ^ { -1 } ~ { } kpc } , respectively ) .
We argue that the X–ray sources are more likely AGN members of the galaxy concentrations .
We set an upper limit for the bolometric luminosity of a hot ICM in the range \sim 0.7 - 2.1 \times 10 ^ { 44 } ~ { } { h _ { 65 } ^ { -2 } ~ { } erg / s } for CLÂ J0533-2411 , depending on the exact redshift .
For EISÂ J0533-2412 the limit is L _ { bol } = ( 6.2 \pm 1.4 ) \times 10 ^ { 43 } ~ { } { h _ { 65 } ^ { -2 } ~ { } erg / s } .
We interpret our result in the following way : EISÂ J0533-2412 ( and possibly CLÂ J0533-2411 ) are proto-clusters and show matter overdensities before collapse , which explains the low significance of extended X-ray emission .