[en] The family Pb2-11 was detected in the multilayer lead XEC with total thickness of 100 c.u. exposed at the Pamirs. Each lead layer was 1 cm thick, the first registering layer being located under 2 cm of Pb(= 4 c.u.). The family comprised a narrow group of gamma-rays which near the maximum of cascade development (= 14 c.u.) produced a dark spot of optical density D approx. .4 over area S = 25 sq.mm. The narrow group of gamma-rays was traced up to the 14th layer corresponding to 30 c.u. Deeper in the chamber, for the space of 70 c.u., no hadron cascade was observed. Thus, a pure electromagnetic halo could be assumed. Preliminary results of the analysis of the family Pb2-11 are presented. The methods of estimation of the energy of the primary particle and the height of nuclear interaction responsible for the observed halo are considered in more detail