In the evening, passersby reported the presence of a human body part in front of the court entrance, a police spokesman said.
“Shortly after we concluded that it was a human head,” the spokesperson said.
Subsequently, a stump presumably of the same corpse was found nearby, on the banks of the Rhine, near the historic customs house.
A distance of about one kilometer separates the two sites where the parts of the body were found.
Police arrested a 38-year-old suspect nearby who they said was known to be involved in drug offenses.
Police added that they believe the suspected perpetrator and the unidentified victim are homeless.