A construction elevator that killed five people when it collapsed in Stockholm last year was missing the bolts that were supposed to hold its mast together, authorities said on Wednesday.

The deadly crash “was caused by failure to perform relevant safety inspections of the hoist assembly,” the Swedish Accident Investigation Authority said.

In the December 2023 accident, the elevator plummeted 20m (66ft) with five people inside, during work on a 14-storey building in the Stockholm suburb of Sundbyberg.

The agency said its probe had showed that five of the nut and bolt assemblies required to hold sections of the elevator’s mast together were missing, leaving the shaft standing only because of friction between its sections.

Before the accident, the mast was extended to the ninth floor. The assemblies were “likely” already missing, the report said.

“The accident occurred when the load on the mast … became greater than the structure could hold, leading to the mast sections separating and the hoist car falling to the ground,” the authority wrote.