  The bulk of neutrons which appear with long delays in neutron monitors nearby
the EAS core (~'neutron thunder'~) are produced by high energy EAS hadrons
hitting the monitors. This conclusion raises an important problem of the
interaction of EAS with the ground, the stuff of the detectors and their
environment. Such interaction can give an additional contribution to the signal
in the EAS detectors at {\em km}-long distances from the large EAS core after a
few $\mu s$ behind the EAS front.
