  Interactions of cosmic ray protons and nuclei in their sources and in the
interstellar medium produce "hadronic" gamma-ray emission. Gamma-rays can also
be of "leptonic" origin, i.e. originating from high-energy electrons
accelerated together with protons. It is difficult to distinguish between
hadronic and leptonic emission mechanisms based on gamma-ray data alone. This
can be done via detection of neutrinos, because only hadronic processes lead to
neutrino production. We use publicly available ten-year IceCube neutrino
telescope dataset to demonstrate the hadronic nature of high-energy emission
from the direction of Cygnus region of the Milky Way. We find a 3-sigma excess
of neutrino events from an extended Cygnus Cocoon, with the flux comparable to
the flux of gamma-rays in the multi-TeV energy range seen by HAWC and LHAASO
telescopes.
