A fatal accident occurred at the Ballincollig Powder Mills on 25 June 1841, when two men were killed by an explosion in the corning house. Little is known about this incident, but two years later another fatal accident took place. Shortly after reporting for work on Saturday, 29 July 1843, John Carol and Jeremiah Long donned their working clothes and special shoes and went to their place of work at the granulating (corning mill). In the building at the time were 21 barrels, each containing of gunpowder. One of the men put the machinery in motion and two minutes later a massive explosion rocked Ballincollig. ""Slates, timber, lead and stones were thrown to a great distance, not a stone in the mill was left standing; even its foundations were torn up and scattered ; and the only part of the machinery standing is a large metal wheel used in the process of granulating. Carrol and Long were killed instantly, their bodies were cast a considerable distance, and in quite different directions. They were wholly denuded of clothes and presented a shocking appearance – mutilated and scarcely recognizable.""