MOSCOW, March 28. /TASS/. A fire in the shopping mall in the Siberian city of Kemerovo was most likely caused by arson in a children’s playground on the fourth floor, a source familiar with the situation told TASS on Wednesday.

"Most likely, the fire was caused by bringing a source of open fire from outside," the source said. These conclusions were made based on the evidence of eyewitnesses.

"The fire broke out in the foamed trampoline pool," the source said. The investigators are also considering other theories.

When the fire started, the alarm, evacuation and smoke ventilation systems were out of work, he said. Most victims were found in a cinema hall and also near the evacuation exits. They were trapped there as the exits and one of the cinema halls had been locked.

Head of the Russian Investigative Committee Alexander Bastrykin told Russian President Vladimir Putin on Tuesday that short circuit was considered as the priority cause of the tragedy. The use of open fire was less likely, he noted.

The fire erupted on the top floor of the Zimnyaya Vishnya (or Winter Cherry) four-storey shopping mall in the Siberian city of Kemerovo on March 25, eventually engulfing an area of 1,500 square meters. According to recent reports, the blaze killed 64 people, including 41 children, and another 76 people were injured.

President Vladimir Putin declared March 28 a national day of mourning for the fire victims.