At least nine children are among the many dead and 16 people are still missing as authorities continue to scour the ash and rubble, according to state news agency Tass.
Fire alarms had not sounded, and staff were reportedly nowhere to be seen as the blaze took hold at the Winter Cherry mall in Kemerovo, a city in Siberia, about 1,900 miles east of Moscow, according to witnesses.
As well as those killed, 11 injured victims are being treated in hospital, suffering from smoke inhalation. Numerous dead and missing were children.
Emergency services said they had extinguished the fire, but later said it had reignited in places, and that rescuers were struggling to recover bodies because the building's top floor had collapsed.
The fire has been contained and a criminal investigation has been launched.
Ten people are still listed as missing.
An eleven-year-old boy, who jumped out of the window of the burning building, remains in critical condition.More news: Europe gets last minute reprieve from Trump tariffs
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The investigators did not give the cause of the fire but said they have obtained evidence proving "flagrant violations" that could have contributed to the heavy loss of life, including the fact that the fire escapes were blocked.
The committee says two other fire safety officials have been detained for questioning, along with the Winter Cherry complex's technical director and the manager of a business located where the fire started.
In a Facebook post (in Russian), Kemerovo politician Anton Gorelkin said that "fire exits were shut, turning the complex into a trap" and "there was no organised evacuation".
The blaze at the shopping centre in Kemerovo, Russia. Some 1,500 square metres of the 23,000 square metre mall were destroyed.
Alexandre Eremeyev, an official with the local Russian emergency services ministry, said in a statement: "This shopping centre on several floors was packed with people at midday on Sunday".
Amid conflicting reports, some have described the source of the fire as the children's playground, suggesting that the trampoline there caught fire after a child allegedly misused a lighter, reports RT News.
Some 200 animals are also believed to have died in the mall's petting zoo.