A fire broke out at an ammunition depot at a U.S. base in southern Baghdad on Tuesday night, setting off a series of explosions from detonating tank and artillery shells that shook buildings miles away. The U.S. military said there were no immediate reports of casualties, reported The Assocaited Press. It was not clear whether the depot at Forward Operating Base Falcon was hit by an attack. The cause of the fire was not immediately known, said Lt. Col, Christopher C. Garver, a military spokesman. Explosions from detonating tank and artillery ordnance and small-arms ammunition stored at the site went off for hours afterward. Large flames and smoke rose from the region, and flashes from the blasts and showers of sparks were visible on the horizon visible several kilometers (miles) away in central Baghdad, where the force of the blasts could be felt. The blasts came at time sporadically, at times in rapid succession, lasting into the night. Helicopters were seen in the night sky flying over the area. The blaze broke out in an ammunition holding area, where material is kept temporarily before distribution to the units at Falcoln, said Lt. Col. Jonathan Withington, a spokesman at the base.