  Purposeful investigation of radiation fluxes strongly delayed in relation to
the main particles front of extensive air shower (EAS) was undertaken at the
Tien Shan Mountain Cosmic Ray Station. It was found that the passage of the EAS
can be accompanied by the delayed thermal neutrons and by the soft $(30-50)$
keV gamma rays, mostly concentrated within a region of about $(5-10)$ m around
shower axis, where the integral radiation fluence can vary in the limits of
$(10^{-4}-1)$ cm$^{-2}$ for neutrons, and of $(0.1-1000)$ cm$^{-2}$ for gamma
rays. The dependence of signal multiplicity on the shower size $N_e$ has a
power shape both for the neutron and gamma ray components, with a sharp
increase of its power index around the value of $N_e\approx 10^6$, which
corresponds to the position of the $3\cdot10^{15}$ eV knee in the primary
cosmic ray spectrum. Total duration of detectable radiation signal after the
EAS passage can be of some tens of milliseconds in the case of neutron
component, and up to a few whole seconds for gamma rays. The delayed
accompaniment of low-energy radiation particles can be an effective probe to
study the interaction of the hadronic component of EAS.
