A 22-year-old man from the city Bielefeld was identified as the potential responsible for a death threat sent to German third-division referee Martin Speckner.
Investigators were able to locate the suspect, they said on Tuesday. Investigations into suspected threats and insults are ongoing.
The criminal investigation department of the state of Hesse and the public prosecutor's office in Frankfurt said on Tuesday that the man wrote an anonymous email after Speckner officiated the Ingolstadt v Arminia Bielefeld match on April 5.
"If we get relegated because of you, you will die. We will find you or your children one day," the 22-year-old allegedly wrote.
According to the German Football Federation (DFB), the author of the email criticized the length of stoppage time, during which Ingolstadt scored the equalizer. The game ended 1-1.
The DFB reported the case to Germany's Central Unit for the Suppression of Internet Crime (ZIT) to file a criminal complaint.
"Death threats and hate messages online are the opposite of fair play," said Andreas Röhrig, president of the criminal investigation department.
"Such insults and threats will not be tolerated. I'm pleased that we were able to quickly bring the suspect out of the anonymity of the internet."