Portuguese officials investigating Wednesday's deadly funicular crash in Lisbon say a cable along the railway's route snapped, but the rest of the mechanism was functioning properly.
After examining the wreckage at the site, it was immediately determined that the cable connecting the two carriages had given way, according to a statement by the national transport safety office.
The brakeman tried to apply emergency brakes but failed to prevent the derailment.
Sixteen people died and about 20 were injured when the upper carriage of the iconic yellow Glória funicular railway crashed into a building.
Five of those killed were Portuguese along with three Britons, two South Koreans, two Canadians, an American, a Ukrainian, a Swiss and a French national.
The 140-year-old funicular is designed to travel up and down Lisbon's steep slopes and is an important form of transport for the city's residents – and a popular tourist attraction.
Although the brakeman activated the pneumatic brakes and a manual brake when the cable came loose, it is unclear whether another automatic brake functioned as intended.
The carriage was traveling at about 60km/h (37mph) when it hit the building.
The seven-page statement also notes that the cable was only 337 days into its expected 600-day operational life.
Investigators are still determining how many victims were on the carriage and how many were on the street. Of those injured, six were admitted to intensive care.
Portugal's Prime Minister, Luis Montenegro, has called the incident "one of the biggest tragedies of our recent past," highlighting the severity and impact of this catastrophic event.