Federal investigators say mistakes by a delivery driver and an employee of a northeast Kansas distilling plant led to the mixing of incompatible chemicals, causing a noxious cloud to spread over Atchison last year.

The U.S. Chemical Safety Board said in a preliminary report issued Wednesday that design and labeling deficiencies at the loading station at MGP Ingredients also contributed to the toxic chemical release of a huge cloud of chlorine gas in October 2016. The release sent about 140 people to hospitals and caused residents in the area to stay indoors or evacuate for several hours.

The agency said the release occurred when a delivery driver mistakenly unloaded sulfuric acid into a tank that contained sodium hypochlorite, releasing thousands of gallons of the gas across the region.]