A train derailment a year ago in the German Alps that left five people dead was caused primarily by damaged concrete ties on the track, investigators said Thursday.

The double-deck regional train derailed on June 3, 2022, shortly after leaving the Alpine resort town of Garmisch-Partenkirchen for Munich. A 13-year-old boy and four women aged between 30 and 70, including two refugees from Ukraine, were killed. More than 70 people were injured, 16 of them seriously.

Germany's federal agency for rail accident investigations said in a preliminary report Thursday that damage to concrete ties used on the line where the accident happened appears to have led to the structure failing and to supports that attach the rails to the ties breaking away, causing the derailment.

GERMANY TRAIN DERAILMENT IN THE ALPS LEAVES AT LEAST 3 DEAD

The ties already had been identified as a potential factor in the derailment in recent months, leading railway operator Deutsche Bahn to launch a "special inspection program" and replace some ties elsewhere as a precaution. The company said Wednesday that it plans to replace some 480,000 ties this year, compared with about 80,000 most years, causing some disruption to trains.