Twenty-nine German police officers were suspended for sharing photos of Adolf Hitler and depictions of refugees in the gas chambers on their phones.
Officers also used far-right chat rooms where swastikas and other Nazi symbols were shared, North Rhine-Westphalia (NRW) officials said.
NRW Interior Minister Herbert Reul said it was a “disgrace to the NRW police”.
Several other episodes of far-right extremism among the German security services follow.
How much the far right caused the earthquake in German politics
- Has Germany done enough to counter far-right violence?
More than 200 police officers were involved in raids on 34 police stations and private homes linked to 11 main suspects. Officers are said to have shared more than 100 neo-Nazi images in WhatsApp groups.
Some of the suspects are accused of spreading Nazi propaganda and hate speech. Others are accused of failing to report the actions of their colleagues.
“This is the worst and most repugnant type of hate speech,” Reul said, adding that he expected the investigation to find more chats with offensive content.
“I am appalled and ashamed,” said Frank Richter, the police chief of the city of Essen, where most of the suspects were. “Words are hard to find.”
Mr. Reul has now launched an investigation into the extent of extremism among the state police.
“Right-wing extremists and neo-Nazis have absolutely no place in the North Rhine-Westphalia police, our police,” he said, and the authorities had to show a “crystal clear political profile” that rejected the far right.
German police and security services have been accused of not doing enough to root out extremists in their ranks.
In July, prosecutors said they arrested a former police officer and his wife suspected of sending threats to well-known immigrants, including several ethnic Turkish lawmakers.
The scandal has already seen Hessian state police chief Udo Münch resign after it emerged that police computers were used to uncover the details of a left-wing politician who later received one of the threatening emails.