A massive fire broke out in a large warehouse used by the biggest online retailer in Russia south of St. Petersburg on Saturday morning.

The fire covered an area of 70,000 square meters (more than 750,000 square feet), with 50,000 square meters (about 540,000 square feet) of the Wildberries warehouse collapsing, according to the Russian Ministry of Emergency Situations. No injuries have been reported.

Videos posted on social media showed employees running down escape stairs and fleeing the scene. A video recorded from a nearby passenger plane showed flames sweeping through the entire warehouse, causing huge columns of smoke to rise into the sky. The Associated Press was not able to immediately verify the authenticity of the videos.

The Russian Ministry of Emergency Situations said firefighters managed to prevent the fire from spreading across the entire warehouse complex area and a power substation, adding that preliminary data indicates the cause of the fire was an electrical wiring fault.