  The giant flare observed on Dec. 27th 2004 from SGR 1806-20 has revived the
idea that a fraction of short (<2 s) Gamma Ray Bursts (GRBs) is due to giant
flares from Soft Gamma Ray Repeaters located in nearby galaxies. One of the
distinguishing characteristics of these events is the thermal (black body)
spectrum with temperatures ranging from ~50 to ~180 keV, with the highest
temperature observed for the initial 0.2 s spike of the Dec. 27th 2004 event.
We analyzed the spectra of a complete sample of short GRBs with peak fluxes
greater than 4 photon s^(-1) cm^(-2) detected by BATSE. Of the 115 short GRBs
so selected only 76 had sufficient signal to noise to allow the spectral
analysis. We find only 3 short GRBs with a spectrum well fitted by a black
body, with 60<kT<90 keV, albeit with a considerably longer duration (i.e. >1
sec) and a more complex light curve than the Dec. 27th 2004 event. This implies
a stringent limit on the rate of extragalactic SGR giant flares with spectral
properties analogous to the Dec. 27th flare. We conclude that up to 4 per cent
of the short GRBs could be associated to giant flares (2 sigma confidence).
This implies that either the distance to SGR 1806-20 is smaller than 15 kpc or
the rate of Galactic giant flares is lower than the estimated 0.033 per year.
