  We present the results of a narrowband search for forming galaxies at high
redshifts. Given the coverage of 276 square minutes of arc, this is the most
extended search for extragalactic emission line objects at near infrared
wavelengths. Despite of flux limits down to 1.4E-16 erg cm-2 sec-1 and of a
total comoving volume surveyed of 1.4E5 Mpc3 (for a cosmolgy with h=0.5 and
q_0=0.5), no such population was detected. We show how this null detection can
be used to derive upper limits to a) the comoving volume density of this
population and b) to the metal production density at redshift between 1 and 4.
