(CNN) A court in Germany has sentenced a 57-year-old man to life imprisonment for poisoning his colleagues' sandwiches.

The man, identified under local law as Klaus O, added dangerous heavy metals to food items at the factory where he worked in the town of Schloss Holte-Stukenbrock over several years, according to CNN affiliate RTL.

The court in Bielefeld, North Rhine-Westphalia, found him guilty of attempted murder Thursday and imposed the maximum custodial sentence.

The judge said the crimes were as serious as murder, according to German news agency DPA.

Two victims have been left with serious kidney damage and a third is now in a vegetative state after falling into a coma, RTL reported.

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