A powerful explosion rocked an ammunition factory near Colleferro, a town about 40 kilometres southeast of Rome, police said on Thursday.
Firefighters and police were at the site and "complex operations" were underway at the Knds Ammo Italy plant which was formerly Simmel Difesa.
Videos shared on social media showed a fire at the factory followed by a massive explosion.
Italian media reported that there were no casualties, with the AGI news agency saying employees sheltered in secure areas at the facility.
The mayor of Colleferro, Giulio Calamita, wrote in a post on Facebook that "the situation is under control."
"The fright is great, but right now it is essential to keep calm and, above all, to avoid spreading untrue information, such as that relating to the 2007 accident which is once again circulating. We will update you as soon as possible with verified information," he wrote.
His post reference a major explosion at the same plant in October 2007which caused killed one worker and left 13 others injured.
The plant is owned by European defence group KNDS and manufactures medium and large-caliber ammunition, Ansa news agency reported.
The Corriere della Sera daily said that the fire started at a compaction press for explosive powder.
