  An upper limit of 16% (at 95% c.l.) is derived for the photon fraction in
cosmic rays with energies greater than 10^19 eV, based on observations of the
depth of shower maximum performed with the hybrid detector of the Pierre Auger
Observatory. This is the first such limit on photons obtained by observing the
fluorescence light profile of air showers. This upper limit confirms and
improves on previous results from the Haverah Park and AGASA surface arrays.
Additional data recorded with the Auger surface detectors for a subset of the
event sample, support the conclusion that a photon origin of the observed
events is not favored.
