Russian President Vladimir Putin on Tuesday visited the scene of a fire in a Siberian shopping mall that killed at least 64 people, 41 one of them children on Sunday.
He laid flowers at a makeshift memorial to the victims of the fire and later met with Kemerovo regional officials.
Putin hit out at "criminal negligence" which he said was to blame for the high death toll. "What's happening here? This isn't war, it's not a spontaneous methane outburst. People came to relax, children," he said.
"We're talking about demography and losing so many people," Putin said in a meeting with ministers in Kemerovo.
"Why? Because of some criminal negligence, because of slovenliness. How could this ever happen?" Putin asked.
The head of Russia's Investigative Committee, which handles major crimes, said the fire alarm system in the mall had been out of order since March 19 and a security guard had not turned on the public address system to warn people to evacuate the building.
The committee said earlier it was trying to bring in the mall's owner for questioning.
"Serious violations (of the law) took place when the mall was being built and when it was functioning. The fire exits were blocked," Svetlana Petrenko, a spokeswoman for the committee, said in a statement on Monday.
Four people have already been detained, including two employees of the firm that services the mall's fire alarm.
Emergency services said they had extinguished the fire, but later said it had re-ignited in places and that rescuers were struggling to recover bodies because the building's top floor had collapsed.
It was unclear whether any people were still unaccounted for.
Health Minister Veronika Skvortsova said from the scene that 13 people were in hospital, including an 11-year-old boy in a serious condition. Russian media said the boy had leapt from a window and that both his parents had been killed.
Many of the victims will only be identifiable by DNA testing, officials said.
An unofficial list of those missing circulating on Russian media included more than 20 children, some as young as five.
Mobile phone messages sent from one of those on the list, 13-year-old Maria Moroz, and published by Russian media, said: "We are burning. I love you all. This is perhaps farewell."