Firefighters said in a statement that the fire broke out early today in a part of the factory used as an illegal dormitory and was brought under control by midday.
The cause was not yet known. Four others were hospitalised.
An ex-military police officer passing by said he notified authorities of the fire.
Leonardo Tuci told the Italian news agency ANSA that he saw smoke coming from the factory and one man trying to put out the flames with a fire extinguisher.