Flowers and dolls are placed outside the doors of the Kemerovo region representative office in Moscow to mourn the victims of the fire at a shopping mall in Kemerovo, in Moscow, Russia, on March 26, 2018. At least 64 people were killed in a fire in Zimnyaya Vishnya shopping mall in south central Russia's Kemerovo city on Sunday. (Xinhua/Evgeny Sinitsyn)

MOSCOW, March 27 (Xinhua) -- A total of 64 people have been confirmed dead in a major fire that broke out at a four-storey shopping mall in Kemerovo city in southwestern Siberia on Sunday, the Russian Investigative Committee said on Monday.

The fire, which erupted on Sunday afternoon, was reported to have been put out by Monday morning after burning for a whole night. Yet video footage showed smoke still rising from the building in the afternoon.

The conflagration, one of the deadliest tragedies in the country in recent years, was believed to have started on the shopping mall's fourth floor, which housed a cinema and children's play area, according to Russian Emergency Services Ministry.

Totally, 25 victims have been identified, including 13 children aged 4-13, said Russian Health Minister Veronika Skvortsova. Witnesses told local media that many children who were watching kids' movies in the mall's cinema were killed.

Minister of Emergency Situations Vladimir Puchkov said he expected 64 to be "the final figure of deaths."

However, the exact number of the missing is still unknown. Previous reports said 64 people were missing, including 41 children.

Rescuers are struggling to reach the upper floors because the roof of the four-story building collapsed.

A total of 663 people took part in the search and rescue operation, the Emergency Situations Ministry said, adding that their work has been complicated by strong gas contamination, high temperatures and dense smoke.

A total of 51 people were provided medical treatment following the incident, according to Sputnik. Thirteen people were hospitalized, including an 11-year-old boy who remained in a grave condition, the Investigative Committee said in a previous statement.

The boy jumped out of a window from the fourth floor and suffered severe injuries, according to Skvortsova. The boy's parents lost their lives in the blaze, Skvortsova said.

The Winter Cherry shopping center, a business complex with a cinema, an indoor skating rink and a petting zoo, is usually packed with people on Sunday afternoon.

So far, five people have been detained and interrogated, including the head of the management company servicing the building and the tenants of the premises where the fire possibly started, the Investigative Committee said.

The investigators were checking information that emergency exits of the shopping mall were blocked when the fire broke out. It also remains undecided whether to detain a guard of the building, who allegedly disabled the warning system of the building.

The Prosecutor General's Office of Russia instructed regional prosecutors to conduct inspections of compliance with fire safety regulations in every shopping complex in Russian regions.

As yet, what caused the deadly blaze remains undetermined.

Several criminal cases were instituted on causing deaths by negligence and violation of fire safety requirements, according to the Russian Investigative Committee.

Russian President Vladimir Putin extended "deep condolences" to the families and friends of the victims on Sunday and ordered related authorities to provide all necessary help.

Kemerovo Regional Governor Aman Tuleyev has signed an order declaring mourning in the region from Tuesday to Thursday.

(Shi Hao in Moscow also contributed to the report.)