Initial investigations into the incident found that the fire was likely “a malicious act”, Italy’s railway infrastructure manager RFI said in a statement.
RFI added that more than 50 technicians had worked to restore burnt cables in the wake of the fire.
Police said the fire may have been related to the ongoing trial of 28 anarchist members in Florence, according to Italian news agency ANSA.
Commuters faced lengthy delays on trains coming from Milan and Bologna in the north and from Rome and Naples in the south.
The news comes at the start of a difficult week for travellers in Italy, with strikes expected to affect all public transport on Wednesday and air travel on Friday.
