German police have arrested a 56-year-old man on suspicion of trying to kill his colleague after he was caught on camera smearing a substance on his workmate's sandwich.
It's led to an investigation into whether the man was responsible for more than 20 deaths at the ARI Armaturen company during his time there.
The latest victim noticed the powder on his food and contacted his manager. CCTV footage showed the suspect spreading the toxic material, The Independent reported.
A chemical analysis revealed it to be lead acetate, a deadly and nearly tasteless poison. Authorities said there was enough of it on the food to cause severe organ damage. After the suspect was arrested a bottle of lead acetate was found in his bag, and mercury, lead and cadmium were found in his apartment.
More than 20 employees at ARI Armaturen have died since 2000, many with symptoms of heavy metal poisoning. Two employees are currently in a coma and another is on dialysis.
"There were a strikingly high number of heart attacks and cancers among the death cases in the company," police said.
A 15-member investigative team was considering exhuming bodies of the deceased as part of the probe, Deutsche Welle reported.