Emergency services rushed to the scene following the explosion, which was loud enough to be heard across several areas of Livorno.
The area was evacuated and teams of firefighters assisted, though no fire was reported.
The area was secured within a couple of hours.
The tank, which was located in the Neri industrial depot specialised in the storage of liquids, is believed to have contained the flammable substance ethyl acetate.
The two men killed were carrying out maintenance duties near the tank, which had reportedly been emptied.
Local media said the victims were employees of local environmental services company Labromare, one aged 52 and the other 25.
One victim died instantly, while the other was still alive when emergency services arrived but could not be resuscitated, Italian daily La Repubblica reported.
With ANSA
