Russian President Vladimir Putin took the unusual step -- for him -- of visiting the Siberian industrial city of Kemerovo, where the tragedy occurred, and faced emotional questions about how so many could have died "because of criminal negligence".
The current toll is at least 64 dead, including 41 children.
Safety exits were blocked, cinema doors were blocked, the fire alarm system was not working and a security guard failed to trigger the public warning system, investigators said.
The regional authorities appeared to have turned a blind eye to violations by the owners of the complex, which included cinemas, a bowling alley and children's play areas, as well as shops and restaurants.
The shopping centre opened in 2013 despite the emergency services having pointed out problems with fire safety. The owners did not make improvements after a 2016 inspection.
It was registered as a business with less than 100 staff in order to reduce official checks.
"Any businessman can tell you how much it costs to make a fire inspector turn a blind eye to violations," wrote popular blogger Ilya Varlamov.
Protests
Opposition leader Alexei Navalny was among several thousand mourners who came to leave flowers on a Moscow square on Tuesday evening.
Some there shouted slogans calling for the sacking of Kemerovo's regional governor Aman Tuleyev and for a "Russia without Putin!"
In Kemerovo, thousands of people spent more than ten hours at a rally on the main square, both confronting officials and mourning the victims.
"Who is really responsible?," "What is the real number of victims?" and "Pawns will be jailed, kings will get away with it" were some of the slogans on placards held by protesters.
The announcement that five people had been arrested, including the owner of the building and the head of the company that managed it as well as one of those in charge of security, was not enough to assuage public anger.
Many in Kemerovo voiced fears that no senior figures would be punished and called for the sacking of top officials including the region's governor Tuleyev.
Rumours swirled that the true total of victims was much higher than had been announced, even prompting the city mayor Ilya Seredyuk to allow a group of protesters to inspect morgues.
Deputy regional governor Sergei Tsivilev went to talk to protesters and confronted one, asking him: "Young man, you're talking to people calmly. What do you want? To get publicity from grief?"
The man, who gave his name as Sergei Vostrikov, then told him he had lost his wife, three children and his sister in the fire and accused him of treating people like "cattle".
Tsivilev then kneeled down to ask for forgiveness for the mistakes that led to the fire.
Vostrikov urged Kemerovo residents to hold another protest on Saturday.
At mourning ceremonies in central Moscow and Saint Petersburg on Tuesday evening, people shouted protest slogans such as "Put Putin on trial, put Tuleyev on trial!"
Blaming opposition
The region's governor Tuleyev, in office since 1997, has failed to visit the scene of the tragedy or meet protesters.
On Monday his first public reaction was not to speak to the public but to thank Putin for personally phoning him to give instructions.
Putin arrived in Kemerovo on Tuesday where he visited the improvised memorial set up by the public and laid flowers. He also held a televised meeting with Tuleyev, the emergency services minister and the country's chief investigator, Alexander Bastrykin.
Tuleyev thanked Putin again and apologised to him personally for what happened. He promised to meet each affected family and to pay off any outstanding debts from loans taken out by victims.
He accused the "opposition" of taking advantage of the situation to feed on "people's grief" and of posing as relatives of the victims.
Russia's main opposition leader Navalny, in his blog, condemned the Kemerovo authorities, who have also put pressure on his supporters in the city, as "a criminal conglomerate, real bandits who think only of personal profit".
He said that rescue workers had used outdated equipment and that there was a lack of proper coordination at the site of the blaze.
Journalist Oleg Kashin, writing on Republic.ru news website, said the tragedy showed the "real -- very low -- price of human life in Russia."
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