  We present the identification of 42 narrow-line active galactic nuclei
(type-2 AGN) candidates in the two deepest observations of the JADES
spectroscopic survey with JWST/NIRSpec. The spectral coverage and the depth of
our observations allow us to select narrow-line AGNs based on both rest-frame
optical and UV emission lines up to z=10. Due to the metallicity decrease of
galaxies, at $z>3$ the standard optical diagnostic diagrams (N2-BPT or S2-VO87)
become unable to distinguish many AGN from other sources of photoionisation.
Therefore, we also use high ionisation lines, such as HeII$\lambda$4686,
HeII$\lambda$1640, NeIV$\lambda$2422, NeV$\lambda$3420, and NV$\lambda$1240,
also in combination with other UV transitions, to trace the presence of AGN.
Out of a parent sample of 209 galaxies, we identify 42 type-2 AGN (although 10
of them are tentative), giving a fraction of galaxies in JADES hosting type-2
AGN of about $20\pm3$\%, which does not evolve significantly in the redshift
range between 2 and 10. The selected type-2 AGN have estimated bolometric
luminosities of $10^{41.3-44.9}$ erg s$^{-1}$ and host-galaxy stellar masses of
$10^{7.2-9.3}$ M$_{\odot}$. The star formation rates of the selected AGN host
galaxies are consistent with those of the star-forming main sequence. The AGN
host galaxies at z=4-6 contribute $\sim$8-30 \% to the UV luminosity function,
slightly increasing with UV luminosity.
