  The origin of the magnetic fields in neutron stars, and the physical
differences between magnetars and strongly magnetised radio pulsars are still
under vigorous debate. It has been suggested that the properties of the
progenitors of neutron stars (the massive OB stars), such as rotation, magnetic
fields and mass, may play an important role in the outcome of core collapse
leading to type II SNe. Therefore, knowing the magnetic properties of the
progenitor OB stars would be an important asset for constraining models of
stellar evolution leading to the birth of a neutron star. We present here the
beginning of a broad study with the goal of characterising the magnetic
properties of main sequence massive OB stars. We report the detection of two
new massive magnetic stars in the Orion Nebula Cluster: Par 1772 (HD 36982) and
NU Ori (HD 37061), for which the estimated dipole polar strengths, with 1 sigma
error bars, are 1150 (+320,-200) G and 650 (+220,-170) G respectively.
