According to a report by broadcaster NDR, one incident saw the police officer choke a refugee from Afghanistan and drag him through the cells with his feet in chains.
In another case he humiliated a refugee from Morocco by force feeding him rotten pork, reports Focus.
The policeman is then alleged to have reported on his abuses to a friend through WhatsApp with messages such as “I beat him down”, “I stuck my finger in his nose” or “I choked him, that was funny”.
He is also alleged to have sent picture of the abuse in which a man can be seen bound in an unnatural position with a clearly pained expression on his face.
According to NDR, investigators searched the man's house as well as the police station on Friday.
Private refugee guards investigated
Meanwhile, prosecutors in North Rhine-Westphalia announced on Monday that they were investigating 50 people over attacks on residents at a refugee home.
The home in Burbach was run by a private company under contract for the state government.
A group of guards responsible for some of the worst abuses were allegedly nicknamed “the SS” by inmates.
One of the attacks in a “problem room” at the centre was filmed by the perpetrators. In the photos the guards posed with their victims.
Since then many more possible abuses have come to light, a spokesperson for the prosecutor said.
As well as guards, state employees are also under suspicion: social workers, the home's administrators and police officers knew about the attacks without reporting them, prosecutors allege.
“We are investigating assault, false imprisonment and coercion,” the spokesman said.
When the investigation will be concluded is still unclear.