A cable linking the two carriages on the iconic Lisbon Gloria funicular snapped, a report into the deadly crash has found.
At least 16 people died and 23 people were injured when the carriage came off the tracks at about 6pm on Wednesday.
Footage from the crash shows the tram-like funicular, which carries people up and down a hillside in the Portuguese capital, destroyed and emergency workers pulling people out of the wreckage.
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, police said.
The carriage had only travelled about six metres when it lost the “balancing force of the connecting cable”.
The vehicle’s brake‑guard immediately “activated the pneumatic brake as well as the manual brake”, the Office for the Prevention and Investigation of Aircraft Accidents and Railway Accidents said.
But the brake did not work, and it crashed at around 60kmh (37mph) within about 50 seconds.
“The violent collision was immediately noticed by bystanders and law enforcement officers present, and emergency services were quickly notified,” the report added.
When assessing the wreckage, inspectors said: “It was immediately clear that the cable connecting the two cabins had given way.”
However, the report suggests maintenance of the equipment was up to date, with a visual inspection carried out on the morning of the accident.
But it notes the area where the cable broke is not visible “without dismantling”.
Analysis of the wreckage also showed the cable had a specified life of 600 days, but at the time of the accident it had 263 days left.
It is still unclear how many victims were travelling on the carriage, which can hold about 40 passengers, and how many were on the street, the document states.
The investigators stress they have not reached “valid conclusions” about the cause of the crash and will provide a full preliminary report within 45 days.
The line, which opened in 1885 and is popular with tourists, connects Lisbon’s downtown area near the Restauradores Square with the Bairro Alto (Upper Quarter), known for its vibrant nightlife. Its two cars are attached to opposite ends of a haulage cable with traction provided by electric motors on the cars that counterbalance each other.
