  Simulations show that neutrons are the most abundant component among
extensive air shower hadrons. However, multiple neutrons which appear with long
delays in neutron monitors nearby the EAS core ('neutron thunder') are mostly
not the neutrons of the shower, but have a secondary origin. The bulk of them
is produced by high energy EAS hadrons hitting the monitors. The delays are due
to the termalization and diffusion of neutrons in the moderator and reflector
of the monitor accompanied by the production of secondary gamma-quanta. This
conclusion raises the important problem of the interaction of EAS with the
ground, the stuff of the detectors and their environment since they have often
hydrogen containing materials like polyethilene in neutron monitors. Such
interaction can give an additional contribution to the signal in the EAS
detectors. It can be particularly important for the signals from scintillator
or water tank detectors at km-long distances from the EAS core where neutrons
of the shower become the dominant component after a few mcsec behind the EAS
front.
