Inspector Lucelio Silva tells the G1 news portal the explosion occurred today in one of the production units of the factory, which is located in a rural part of the municipality of Santo Antonio do Monte in the state of Minas Gerais.
He said the four people killed were women working in the factory. Two women suffered minor injuries and one man was hospitalized with burns to his back.
Silva said the investigation into the cause of the explosion will last about 30 days.