A female German student has been arrested on suspicion of poisoning seven people at a university last August.
A 32-year-old woman with psychiatric problems was detained on Thursday, German investigators confirmed.
"There is a suspicion that the defendant ... is not responsible for her actions due to a mental illness," the police and the prosecutor's office of Darmstadt said in a joint statement.
The student -- who is from Mainz -- has been detained in a psychiatric institution and has not commented on the allegations, authorities added.
She had been studying Materials Science at the Technical University in Darmstadt in western Germany since 2017.
Seven people at the university were left with "serious health problems, including symptoms of poisoning" after the incident in August 2021.
One of the victims -- a 30-year-old student -- was initially said to be in a "critical" condition between life and death.
The 32-year-old is accused of adding harmful substances into food and drink on campus.
Investigators found that the woman had probably entered the university building in question the night before the poisoning incident. Authorities believe the student had felt "felt persecuted by the employees in question".
The "harmful substances" involved in the suspected poisoning have not been identified.