SCHLOSS HOLTE-STUKENBROCK, GERMANY – Police believe a man killed at least 21 of his co-workers by poisoning their lunches.

The Mirror reports a 56-year-old German man was arrested after he was caught putting a suspicious powdery substance on the lunch of a colleague.

Officials say the unidentified suspect is believed to have killed his co-workers over an 18 year period. An investigation showed 21 employees at the same company had died of heart attacks or cancer before they retired.

Police found toxic chemicals in the man's apartment during a search.