The fire, which broke out before dawn, engulfed 18,000 square meters of the MEGA Khimki mall at its peak. It was eventually contained at 7,000 square meters two hours later, reports The Moscow Times.

Several videos of the fire have gone viral on social media.

“The building’s structural features and a large combustible load complicated efforts to extinguish the fire,” Russia’s Emergency Situations Ministry said in a social media update as quoted by The Moscow Times.

“The fire spread rapidly over a large area due to the formation of strong convection currents from the collapse of the roof and instant access to oxygen,” it said.