  A complete understanding of the mass assembly history of structures in the
universe requires the study of the growth of galaxies and their supermassive
black holes (SMBHs) as a function of their local environment over cosmic time.
In this context, it is important to quantify the effects that the early stages
of galaxy cluster development have on the growth of SMBHs. We used a sample of
Herschel/SPIRE sources of $\sim$ 228 red and compact Planck-selected
protocluster (PC) candidates to estimate the active galactic nuclei (AGN)
fraction from a large sample of galaxies within these candidates. We estimate
the AGN fraction by using the mid-infrared (mid-IR) photometry provided by the
WISE/AllWISE data of $\sim650$ counterparts at high redshifts. We created an
AllWISE mid-IR colour-colour selection using a clustering machine learning
algorithm and two {\it WISE} colour cuts using the 3.4 $\mu m$ (W1), 4.6 $\mu
m$ (W2) and 12 $\mu m$ (W3) passbands, to classify sources as AGN. We also
compare the AGN fraction in PCs with that in the field to better understand the
influence of the environment on galaxy development. We found an AGN fraction of
$f_{AGN} = 0.113 \pm 0.03$ in PC candidates and an AGN fraction of $f_{AGN} =
0.095 \pm 0.013$ in the field. We also selected a subsample of `red' SPIRE
subsample with a higher overdensity significance, obtaining $f_{AGN} = 0.186
\pm 0.044$, versus $f_{AGN} = 0.037 \pm 0.010$ of `non-red sources', consistent
with higher AGN fractions for denser environments. We conclude that our results
point towards a higher AGN fraction in PCs, similar to other studies.
