Members of the emergency ministry fire service try to put out the fire at the Zimnyaya Vishnya shopping mall in Kemerovo, Russia, on March 25, 2018. (Xinhua/Sputnik)

MOSCOW, March 26 (Xinhua) -- A total of 64 people have been confirmed dead in a major fire that broke out at a shopping mall in Kemerovo city in southwestern Siberia one day ago, the Russian Investigative Committee said Monday.

The fire, which started Sunday afternoon, was reported to have been put out by Monday morning, but video footage showed smoke rising in the afternoon from the building that was still smoldering.

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

The committee said the death toll has climbed to 64, among whom 15 victims have been identified.

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.

Witnesses told local media that many children who were watching kids' movies in the mall's cinema were killed.

A total of 44 people were provided medical treatment and 10 of them remained in hospital, the Investigative Committee said in a previous statement.

An 11-year-old boy who jumped out of a window from the fourth floor suffered severe injuries, according to Health Minister Veronika Skvortsova.

The Winter Cherry shopping center, a business complex with a cinema inside, is usually packed with people on Sunday afternoon.

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

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

The investigators were checking the information that fire exits of the building were blocked when the fire broke out, it said, adding that it was deciding whether to detain a guard of the building, who allegedly disabled the warning system.

Russian President Vladimir Putin extended 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.