  X-ray surveys of the Carina nebula have revealed a few hard and luminous
sources associated with early-type stars. Such unusual characteristics for the
high-energy emission may be related to magnetically-confined winds. To search
for the presence of magnetic fields in these objects, we performed a limited
spectropolarimetric survey using the FORS instrument. The multi-object mode was
used, so that a total of 21 OB stars could be investigated during a
one-night-long run. A magnetic field was detected in two objects of the sample,
with a 6 sigma significance; Tr16-22 and 13. Such a detection was expected for
Tr16-22, as its X-ray emission is too bright, variable and hard, compared to
other late-type O or O+OB systems. It is more surprising for Tr16-13, a poorly
known star which so far has never shown any peculiar characteristics.
Subsequent monitoring is now needed to ascertain the physical properties of
these objects and enable a full modelling of their magnetic atmospheres and
winds.
