BERLIN (AP) — Seven people at a university in western Germany have received medical treatment after showing symptoms of poisoning, and prosecutors have opened an investigation into suspicions of attempted murder, authorities said Tuesday.

The employees and students at the Technical University in Darmstadt, south of Frankfurt, experienced medical problems on Monday. Police say that milk cartons and water containers in one of the buildings on the campus appear to have been contaminated with a harmful substance between Friday and Monday. The contaminated liquid was said to have a powerful smell.

Police and prosecutors said Tuesday that they had searched other university buildings as a precaution but found nothing else linked to the suspected poisoning. They also said no one else had come forward with symptoms.

They said in a statement that they are doing everything to “identify the culprit or culprit” and that, as far as they are aware, there is no longer any “acute danger.”

Prosecutor Robert Hartmann told reporters that, while authorities believe the contamination may have been deliberate, they currently have no information pointing to any specific person as a possible culprit. He said that the substance has been identified, but prosecutors won’t publicly name it for now in view of the ongoing investigation.

One person was affected “relatively severely” by the poisoning, but their life apparently is no longer in danger, Hartmann said.

“We are shocked by the apparent crime that took place at our university,” the university’s president, Tanja Bruehl, said in a statement.