Before leaving, Dyatlov had agreed he would send a telegram to their sports club as soon as the group returned to Vizhai. It was expected that this would happen no later than 12 February, but Dyatlov had told Yudin, before he departed from the group, that he expected it to be longer. When the 12th passed and no messages had been received, there was no immediate reaction, as delays of a few days were common with such expeditions. On 20 February, the travellers' relatives demanded a rescue operation and the head of the institute sent the first rescue groups, consisting of volunteer students and teachers. Later, the army and militsiya forces became involved, with planes and helicopters ordered to join the operation.