The train was 8 kilometers into the Apennine Base Tunnel, on the Florence-Bologna line near Vernio, on a long straight stretch with speed limits of up to 160 km/h at the time, and was travelling at 150 km/h.

Its shock wave, reflected by the tunnel sides, blew out all the window glass and internal doors, throwing shrapnel-like shards into the compartments.

Train conductor Gian Claudio Bianconcini – on his last journey before retiring – was wounded in the nape of his neck, but managed to reach a service telephone and call for help.

A diesel-electric engine was brought from Bologna to recover the head section of the damaged train, allowing rescuers to reach the blown-up coach.

Coaches of a rescue train were used as ambulances, ferrying the injured and taking them to San Benedetto Val di Sambro-Castiglione dei Pepoli railway station.

After the train departed, a woman was found in shock in the tunnel cavity, and was taken on foot to the nearby Ca' di Landino station.

Official suspicion centered on neo-fascist terrorists, since the attack took place on the same railway stretch at which right-wing extremists bombed the Italicus train in 1974, killing twelve and wounding 48.

In March 1985, Mafia boss Giuseppe Calò and Guido Cercola were stopped in Rome and jailed for crimes related to drug trafficking.

Calò had ties with P2 masonic lodge and the Banda della Magliana, and was a well known to many Italian terrorists, including Cristiano and Valerio Fioravanti, Massimo Carminati and Walter Sordi.

The Florence Criminal Court found Pippo Calò, Cercola and people linked to them (Alfonso Galeota, Giulio Pirozzi and Camorra boss Giuseppe Misso) guilty on 25 February 1989, sentencing them to life imprisonment for massacre.

Giulio Pirozzi and his wife were saved by a police car which fortuitously passed on the opposite lane, causing the killers to flee.

The Corte di Cassazione confirmed the sentences on 24 November 1992, officially recognizing a "coordinated hand by the Mafia" in the disaster.

On 18 February 1994, Florence Court discharged MSI member of Parliament Massimo Abbatangelo from the massacre charge, but deemed him guilty of giving the explosive to Misso in early 1984.

[3] Prosecutors said that the explosive used to carry out Train 904 attack were the same used to kill Antimafia judge Paolo Borsellino and his escort in via D'Amelio on 19 July 1992.