Russian officials have warned it is unlikely that any of the 64 workers trapped within Russia’s largest hydro-electric power plant will survive following a blast earlier this week.

12 people have already been confirmed dead after the explosion at the Sayano-Shushenskaya power plant in Siberia.

Emergencies Minister Sergei Shoigu said groups of divers were searching for survivors in the flooded turbine hall, said the BBC.

The cause of the blast remains unknown but according to local reports, some investigators believe a transformer exploded during repairs at the site where flooding had occurred.

The plant’s owners, RusHydro, said a detailed 3-D map of where its employees were at the time was being used during rescue efforts, according to the BBC.