This enabled investigators to rule out that the blast on Monday that killed five workers and injured nine others was caused by sabotage.

Meanwhile, prosecutors confirmed on Wednesday that they have opened an investigation into charges of multiple manslaughter, culpable building collapse or other disasters and culpable removal of safeguards against work-related accidents.

The Eni depot at Calenzano was undergoing maintenance work on components of the facility that had needed it for years, according to the first inspections ordered by prosecutors just 48 hours after the explosion.

The blast occurred at platform number six of the site’s loading area.

Prosecutors are investigating all the details involving maintenance work to determine the cause of the blast.

Petrol, diesel and kerosene were received and stored at the 170,300- square-metre Calenzano facility and then distributed from it.

The plant is connected to Eni’s Livorno refinery via two pipelines.

Eni said the facility had been operating since 1956 and had 24 tanks and 10 loading platforms.

ANSA