A massive explosion at a food dye factory in Louisville, Kentucky on Tuesday left two people dead and a dozen others injured, as smoke billowed out of torn metal structures and rubble.

The blast at Givaudan Colour Sense killed two people and injured 11 others. Neighbors said they have smelled an ammonia-like odor, a burnt sugar smell and a burnt caramel smell coming from the plant over the years.

Two employees have died following an explosion at a Louisville factory that caused a partial collapse of the building and blew out windows in nearby homes and businesses, the company said Wednesday.