Some 4,000 birds died on 12 February alone at the poultry farm near the capital, Makhachkala.
Samples from the dead birds have been sent for laboratory analysis in Moscow.
Daghestan officials have dismissed concerns of a possible outbreak of bird flu, saying no cases of bird flu have been registered in the republic.
Officials said the Makhachkalinskaya poultry farm is located near another poultry farm where earlier this month some 300,000 chicken died of Newcastle disease, a highly contagious viral disease that strikes poultry.
(Interfax, AFP)