In 1280, a large store of gunpowder at Weiyang in Yangzhou accidentally caught fire, producing such a massive explosion that a team of inspectors at the site a week later deduced that some 100 guards had been killed instantly, with wooden beams and pillars blown sky high and landing at a distance of over 10 li (~2 mi. or ~3 km) away from the explosion, creating a crater more than ten feet deep. One resident described the noise of the explosion as if it "was like a volcano erupting, a tsunami crashing. The entire population was terrified." According to surviving reports, the incident was caused by inexperienced gunpowder makers hired to replace the previous ones, and had been careless while grinding sulfur. A spark caused by the grinding process came into contact with some fire lances which immediately started spewing flames and jetting around "like frightened snakes." The gunpowder makers did nothing as they found the sight highly amusing, that is until one fire lance burst into a cache of bombs, causing the entire complex to explode. The validity of this report is somewhat questionable, assuming everyone within the immediate vicinity was killed.