The causes of the train tragedy in Italy included wartime black market trading, the use of a coal-burning locomotive, and a lack of coordination among the train crew.

In 1943/44, the Allies liberated the southern parts of Italy and progressed slowly but steadily towards Rome amidst continuous and heavy struggles. Worse yet, the country was torn in two: the north, led by fascist Mussolini, and the south, allied with the Allies and led by Victor Emmanuel III, which plunged into a state of civil war. The wartime scarcity brought forth numerous difficulties and gave rise to flourishing black markets. Illegal traders used night trains, which were less monitored, to transport their goods.

On the evening of March 2, 1944, train number 8017 set off with 4 passenger and 43 cargo cars, officially weighing 520 tons. In the first hour of the journey, between Battipaglia and Metaponto station, the electric locomotive was replaced by two steam engines. The train passed through several towns, where an unknown number of passengers including likely many black marketeers boarded with baggage, significantly increasing the weight of the train.

Compounding the difficulties was the use of poor-quality fuel, which produced large quantities of colorless, odorless, and toxic carbon monoxide as a combustion byproduct.

In February 1944, there had already been a poisoning accident in one of the tunnels on the Battipaglia Metaponto line caused by this issue.

At midnight, train 8017 reached the Balvano-Ricigliano station, which was its final stop before the tragedy. Here, a fifty-minute routine maintenance and water replenishment were performed before proceeding further. The next station was Bella Muro, located seven kilometers away, which customarily signaled Balvano when a train had passed through the Armi tunnel. However, no notification was received from train 8017.

The Armi tunnel, at 1968 meters long with a 1.3% gradient, was the site of the disaster. The train, overloaded, could only travel at 15 km/h and slowed down on the moisture-laden tracks in the rising tunnel until it came to a complete stop with almost all the cars inside the tunnel.

The poor-quality coal burned in the confined space left no chance for survival. The driver of the rear locomotive attempted to reverse, but the driver of the front one continued to move forward, and they were unable to communicate with each other. The situation was exacerbated when the crew shoveled more coal into the fire in an attempt to get the train moving.

The crew near the fire were the first to succumb to the suffocating fumes, followed by the people sleeping in the rear cars, the majority of whom never woke up. The few survivors mostly emerged from cars that had not yet entered the tunnel.

It wasn't until 5:10 AM that the Balvano station master learned of the disaster and only about forty individuals were saved, while of the approximately 520 dead, only 235 were identifiable.

Only two crew members survived the catastrophe. The victims were buried without ceremony in four mass graves near Balvano. The Italian authorities only dared to release the details of the incident seven years after the accident, and the survivors and the victims' families continued to receive compensation for an additional twenty years. Due to the lengthy silence, the details of the Balvano disaster such as the causes of the accident, the exact number of victims, and the identities of those responsible remain a subject of debate to this day.