Twenty-two of the dead have been identified following the blast on New Year's Eve, which caused part of the 10-storey building to collapse in Magnitogorsk, a city of about 400,000 just over 1,000 miles from Moscow.
The Russian emergency situations ministry said six children were among the dead.
Six people have been rescued from the rubble, including 11-month-old Ivan Fokin after nearly 36 hours buried under the collapsed building.
But officials have said the odds of finding anyone else alive in the debris look increasingly slim, with temperatures dropping to as low as -24C (-17F).
Footage showed the baby boy taken out from under the rubble before a medical worker quickly injected him with something and he was whisked away.
Ivan was in an extremely serious condition with fractures, a head injury, hypothermia and frostbite, officials said.
He was flown to a hospital in Moscow and is now in a stable condition.
His father Yevgeny told Russian TV that the rescue was a "New Year's miracle".
His mother Olga managed to escape the building's collapse with her other son, aged three.
Rescue worker Pyotr Gritsenko said Ivan had been found after one of the crew heard faint cries.
"They stopped all the equipment, he began to cry louder," he said.
But a search dog and help from Ivan's father were still needed to pull the infant to safety.
Russian President Vladimir Putin travelled to the site of the explosion on Monday and visited the injured in hospital.
Some 110 people lived in the building, according to the RIA news agency.
Deputy emergency minister Pavel Baryshev said: "We must work as quickly as we can as temperatures don't give us any time to linger."
The blast reportedly happened at around 6am local time, when many people were sleeping on what was a Russian public holiday.