Three central Rome metro stations are currently closed.
Rome's central train station Termini has closed one of its escalators after smoke was seen coming through the escalator steps leading to the restaurant area Terrazza Termini.
There was nobody injured in the incident which took place during the afternoon of Saturday 30 March.
The smoke is believed to have come from the plant's engine, according to local media reports.
The incident comes as the city battles with malfunctioning escalators which have resulted in the closure of three central underground stations: Repubblica, Barberini and Spagna.
In recent days the city revoked its contract with the metro maintenance firm as the situation escalated with the closure of Spagna station on 23 March.
Repubblica, which closed after a major accident involving dozens of injuries, has been shut since 23 October.