There are now fears that the tens of thousands of tonnes of oil may ignite, the Daily Mail reported, as firefighters continued to work to battle the blaze.
"The fire occurred inside refinery Italian ENI energy company occurred around 15:40 (local time), causing a large fireball of tens of meters,” the Italian Department of Civil Protection in the province of Alessandria said in a statement.
Residents who witnessed the explosion quickly posted photos and videos to social media.
No injuries have been reported, according to a statement from the Italian oil company.
The cause of the fire remains unknown.
esplosione raffineria #sannazzaro pic.twitter.com/iBcliLuK3D
— Graziano Sida (@gra_67) 1 December 2016
Si vede da casa mia.
— L'ALE ® (@snailale) 1 December 2016
30km
#Sannazzaro pic.twitter.com/tnrTjqztGj
More about: