Neutron bursts in EAS: New physics or nuclear physics?

An analysis has been done of events with very high multiplicity of neutrons (neutron bursts) observed in two experiments with neutron monitor triggered by EAS: at Mexico City and at Baksan. The explanation of the phenomenon of delayed by milliseconds pulses can be found in neutron physics, while the origin of EAS with abnormally high multiplicity of neutrons is still a question. Monte Carlo simulations of slow neutron flux using known cross sections and real geometry of the experiments show rather good agreement with observed data.