  The recent HESS detections of supernova remnant shells in TeV gamma-rays
confirm the theoretical predictions that supernova remnants can operate as
powerful cosmic ray accelerators. If these objects are responsible for the bulk
of galactic cosmic rays, then they should accelerate protons and nuclei to
10^15 eV and beyond, i.e. act as cosmic PeVatrons. The model of diffusive shock
acceleration allows, under certain conditions, acceleration of particles to
such high energies and their gradual injection into the interstellar medium,
mainly during the Sedov phase of the remnant evolution. The most energetic
particles are released first, while particles of lower energies are more
effectively confined in the shell, and are released at later epochs. Thus the
spectrum of nonthermal paticles inside the shell extends to PeV energies only
during a relatively short period of the evolution of the remnant. For this
reason one may expect spectra of secondary gamma-rays and neutrinos extending
to energies beyond 10 TeV only from T \lesssim 1000 yr old supernova remnants.
On the other hand, if by a chance a massive gas cloud appears in the \lesssim
100 pc vicinity of the supernova remnant, ``delayed'' multi-TeV signals of
gamma-rays and neutrinos arise when the most energetic partices emerged from
the supernova shell reach the cloud. The detection of such delayed emission of
multi-TeV gamma-rays and neutrinos allows indirect identification of the
supernova remnant as a particle PeVatron.
