Of the three people originally saved from the explosion, a woman later died in hospital.
Earlier the ministry only identified as seven people missing, but an eighth was found late in the afternoon.
The rescue work took place in icy temperatures of below minus 20 degrees Celsius.
'Huge bang'
Television pictures showed emergency rescue workers and machinery searching for survivors in the smouldering rubble of the apartment building as shocked locals looked on.
A witness from a nearby apartment told Russia's Channel One television: "A huge bang woke me up and glass began to shower down on me. I went onto the balcony and I heard screaming. Everything was on fire."
A woman who lived in the building told the Russian Vesti-24 television station: "We found our grandmother but we are still missing our grandfather and our seven-year-old girl."
The explosion happened shortly after midnight on Wednesday.
Such incidents have become commonplace in Russia's ageing apartment buildings.