It happened in the branch to Rada Tilly that extended alongside the coast, part of the Comodoro Rivadavia Railway and then operated by Ferrocarriles Argentinos.

[2] The single-unit railbus (numbered "52") was about to reach Comodoro Rivadavia when it took a sharp curve, known in the neighborhood as the "sulfa", where the sheds of the Sagosa company stands nowadays.

The high speed (80 kilometres per hour (50 mph)) of the train, the exceeded number of passengers (there were 100 people when the maximum capacity of the coaches were 48), and the 750 mm narrow gauge's insability caused the railcar to be derailed, falling from a 40-metre (130 ft) hillside in a zone known as playa 99, a beach resort in Punta Piedras.

The number of deaths would continue to grow due to another accident in the rescue operative, when the crane fell off while raising the train, resulting in more fatal victims.

[8] One year before, the military government led by Jorge Videla had promulgated a decree that closed a high number of rail services in Argentina due to their low profitability,[9] being the CRR one of the several lines affected.