MOSCOW (AP) — A huge fire tore through a large warehouse used by Russia’s largest online retailer south of St. Petersburg on Saturday morning.

The blaze covered an area of 70,000 square meters (more than 750,000 square feet), with 50,000 square meters (around 540,000 square feet) of the Wildberries warehouse collapsing, according to Russia’s Emergency Situations Ministry. No casualties were reported.

Videos posted to social media appeared to show employees running down fire escapes and fleeing the scene. A video shot from a passenger jet flying nearby showed flames totally engulfing the warehouse, sending huge plumes of smoke into the sky. The Associated Press couldn’t immediately verify the authenticity of the videos.

Russia’s Emergency Situations Ministry said that firefighters had been able to prevent the fire from spreading across the entire area of the warehouse complex and to an electrical substation. It said that, according to preliminary data, the cause of the fire was faulty electrical wiring.