  We searched for X-ray flashes (XRFs) -- which we defined as ~10s duration
transient X-ray events observable in the 0.4-15 keV passband -- in fields
observed using XMM-Newton with the EPIC/pn detector. While we find two
non-Poissonian events, the astrophysical nature of the events is not confirmed
in fully simultaneous observations with the EPIC/MOS detectors, and we conclude
that the events are anomalous to the EPIC/pn detector. We find a 90% upper
limit on the number of flashes per sky per year at two different incoming flash
fluxes: 4.0x10^9 events / sky / year for a flux of 7.1x10^-13 erg / cm^2 / s
and 6.8x10^7 events / sky / year for 1.4x10^-11 erg / cm^2 / s. These limits
are consistent with an extrapolation from the BeppoSAX/WFC XRF rate at much
higher fluxes (about a factor of 10^5), assuming an homogenous population, and
with a previous, more stringent limit derived from ROSAT pointed observations.
