Police described the incident on the tram as "unusual behavior." The woman is now being investigated for assault.
A woman traveling without a ticket on a local tram line is being investigated for assault for spraying a ticket controller with breast milk, German police said Monday.
The 31-year-old woman was traveling with a male companion in the western city of Gelsenkirchen on Saturday when a ticket inspector requested their identification and told them to get off at the next stop.
"During the identification process, the woman exposed her breast and sprayed the ticket controller with breast milk," police said in a statement.
The surprise mother's-milk diversion allowed the man traveling with her to flee the scene.
Alarmed police officers later arrived at the scene to find the woman resisting to provide her personal details, forcing police to pin her to the ground.
She was taken to the police station and later released, but not before police initiated a criminal complaint for riding without a ticket and grievous bodily harm.