Employees at the Technical University of Darmstadt said they began experiencing medical problems on Monday after reportedly drinking beverages from the university’s L2.01 building.
The victims experienced discomfort and discolouration before being taken to hospital on Monday, according to police.
Police said several milk cartons and water containers appeared to have been contaminated with a harmful substance between Friday and Monday.
The contaminated liquid was said to have had a powerful smell.
Numerous food and water samples were taken for laboratory testing, according to local reports.
In a statement shared on Twitter, local police said: “So far, we know of seven people who, after consuming various foods and beverages in the ‘L201’ building of the Technical University, have shown signs of poisoning, among other things.”
The university’s president Tanja Bruehl said in a statement: "We are shocked by the apparent crime that took place at our university.
"After initial investigations by the police, those affected are believed to have been victims of a poison attack. I will contact them personally as soon as possible, if their condition allows it."
Police and prosecutors said they searched other university buildings as a precaution but found nothing else connected to the suspected poisoning.
They also said no one else had come forward with symptoms.
The force said in a statement that they are doing everything to "identify the culprit or culprits" and that, as far as they are aware, there is no longer any "acute danger".
Prosecutor Robert Hartmann said while authorities believe the contamination may have been planned, they currently have no information pointing to any specific person.
He added that the substance has been identified but prosecutors will not publicly name it for now in view of the ongoing investigation.