  We are studying the extremely young cluster of M17 to investigate the birth
of high-mass stars and the initial mass function. Deep JHKL imaging and K-band
spectroscopy from the VLT of 201 stars toward the cluster is presented. The
majority of 104 stars show the CO band-head in absorption. Half of them emit
X-rays and/or have infrared excess, indicative of very young objects. Their
intrinsic IR luminosity is compatible with intermediate and high-mass pre-main
sequence stars. Nine additional stars have the CO feature in emission, while
sixty sources are lacking any stellar spectral feature due to veiling by
circumstellar dust. We suggest that CO absorption is - as in the case of
low-mass stars - also a common feature during the early evolution of stars with
higher masses. According to model calculations the observed CO absorption is
most likely a sign of heavily accreting protostars with mass accretion rates
above 10^-5 solar masses/yr.
