(CNN) Mourners at a German funeral were accidentally served a drug-laced cake, police said.

After a funeral in Rostock, attendees convened at a restaurant to indulge in some cake -- one of which contained hashish, a potent drug made from the resin of cannabis plants, Rostock police spokesman Christopher Hahn told CNN.

Grief gave way to nausea and dizziness, and 13 of the guests fell ill shortly after unknowingly ingesting the drug . Their symptoms sent several of them to the ER, including one guest whisked away in an ambulance, Hahn said.

The baker was revealed to be a restaurant employee's 18-year-old daughter. She regularly baked cakes for events there, Hahn said, and her mother accidentally brought in the frozen hash cake along with several other drug-free ones in the family's fridge.

"She had baked it with another event in mind," Hahn said.

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