A truck hauling ammonium nitrate crashed Tuesday morning in Rockcastle County, spilling about 24 tons of the chemical in and around a nearby creek. Emergency management officials said the rollover crash happened before 10 a.m. along Mullins Station Road east of Mount Vernon. Environmental cleanup crews also responded. Ammonium nitrate, typically used as a high-nitrogen fertilizer, is mildly toxic to the touch and can be explosive under certain conditions. Officials said an “unknown amount” of the substance may have entered nearby Roundstone Creek.