Watch out for mystery treats at your workplace- sandwiches made with poisoned bread were left as a "gift" for unsuspecting employees of a German auto parts company yesterday morning. Later that day, 25 of them were hospitalized, police told the Associated Press.

Police spokesman Frank Soika told the AP that the hospitalization was a precautionary measure, and none of the 25 people showed signs of sickness after eating the poisoned bread, which was laced with rodenticide.

According to the Telegraph, a mysterious box of cheese and sausage sandwiches was left on the doorstep of the Mueller Technik auto parts company in Steinfeld, a northwestern German town in Lower Saxony, on Tuesday morning, along with a note stating that they were a gift to employees.

The auto workers helped themselves throughout the morning, until later in the afternoon when one of the workers noticed a strange substance on the bread and contacted the police.

Later that night, a Berlin laboratory confirmed that the bread had been sprinkled with rat poison. The Telegraph reports that everyone who ate the poisoned bread was hospitalized for observation.

Many rat poisons contain anticoagulants like warfarin, which kills rodents by causing massive internal hemorrhaging. The Environmental Protection Agency (EPA) reports that such chemicals are less toxic to humans, but can still cause nosebleeds, bleeding gums, and anemia within days of ingestion. Severe poisoning can cause death from shock, and ingesting as little as 1 mg of the most potent warfarin is toxic to an adult.

With that in mind, the German workers were lucky. "We don't believe the amount of poison used would have been deadly, but it could have caused serious illness," Soika told the AP.

It's still unclear who left the poisoned sandwiches in Steinfeld, and why. Soika told the Telegraph that employees at the German company had a regular tradition of getting sandwiches for each other.

That raises the possibility of a disgruntled employee, though the Telegraph reports that Helmut Kohake, the company director, held a press conference on Wednesday to state that that he was unaware of any discontentment among workers.

The unsettling incident should remind everyone to be wary of unaccountable food like the mystery sandwiches. The poisoned bread may not have harmed any of the German workers, but it doesn't hurt to scrutinize unfamiliar food before eating it.

"You don't know whether something like this could happen again," Kohake said in the press conference.