LISBON, Portugal (AP) — The failure of a steel cable and maintenance flaws contributed to the crash of a streetcar in the Portuguese capital Lisbon last month that killed 16 people and injured 21 others, according to an official preliminary report published Monday.

The streetcar’s derailment is one of Lisbon’s worst tragedies in recent memory. The century-old streetcar, called a funicular because it travels up an down a steep hill in tandem with a second car, is a popular city tourist attraction.

The streetcar at the time hurtled down the hill before coming off the rails on a bend and smashing into a building, leaving the wooden cabin a crumpled wreckage. Police said that 11 of those killed were foreigners.

The Office for Air and Rail Accident Prevention and Investigation, a government body, said in the report the underground steel haulage cable which connected the two cars and balanced out their weight, wasn’t strong enough for the job. It wasn’t certified for public transport nor installed in accordance with the manufacturer’s instructions, according to the report.

The cable had been in use for less than a year.

The investigation identified five instances when the maintenance program referred to “non-existent, inapplicable or outdated standards,” the report said.

After the cable broke, safety systems cut power to the streetcar, meaning that the pneumatic brake no longer worked and the manual brake wasn’t strong enough to stop the car hurtling down the hill. The investigation is also looking into whether streetcar brakes need to be improved.

The preliminary report is not intended to determine liability or establish blame, the investigating body said.

A fuller and more detailed final report resulting from closer analysis of the accident is expected next year.