An Adolf Hitler speech shown in a 1935 Nazi propaganda film was broadcast over Chicago police radios in an unauthorized audio transmission.

The audio which started playing on Wednesday night appears to be from a speech made by the Nazi leader in Leni Riefenstahl's 'Triumph of the Will', according to Imke Meyer, a professor at the University of Illinois at Chicago who teaches Germanic studies.

'Numerous key words were audible, among them 'Deutschland' (Germany), 'Partei' (party), 'Volk' (the people — the German people would be referenced in this context), 'Jahrtausende' (millennia — a reference to the idea that the Third Reich would endure for thousands of years to come), 'Reich' and 'Fuhrung' (leadership),' Meyer explained to the Chicago Tribune.

The audio - that played for four minutes - appears to be from a speech made by the Nazi leader in Leni Riefenstahl's 'Triumph of the Will'

Radio frequencies were down for approximately four minutes while the transmission played

The 1935 film features footage from Hitler at a 1934 Nazi Patry Congress event. Riefenstahl had been commissioned by the Third Reich to make the motion picture showing how well the party was doing.

Radio frequencies were down for approximately four minutes while the transmission played.

The 1935 film features footage from Hitler at a 1934 Nazi Patry Congress event and was commissioned by the Third Reich

According to Melissa Stratton, spokeswoman for the Office of Emergency Management and Communications, asserted that the unauthorized transmission was a 'rogue radio transmission.'

She added that the city is investigating the incident but made clear that a city user had not accidentally blasted the audio.

Users on Twitter known for listening to Chicago police scanners noticed the transmission as well.

One user noted that the transmission had moved channels, adding that cheap radios have the capability to interfere with police transmissions.

Stratton claimed that the transmission included 'the part of the film that presents Hitler's closing speech at the convention.'

Riefenstahl had been commissioned by the Third Reich to make the motion picture showing how well the party was doing

One Twitter user noted that the transmission had moved channels, adding that cheap radios have the capability to interfere with police transmissions

During the transmission, a radio dispatcher told police to switch their channels if they had any emergencies.

'We have a rogue radio,' the dispatcher said.

That same dispatcher later added: 'A little bit of an officer safety hazard on the zone at the moment, so anybody with any emergency please switch over to a citywide.'

These types of transmissions happen 'periodically,' Stratton explained, 'but we have worked with the police and federal authorities to investigate when it has occurred.'

If there is a 'substantial issue' with a channel, police will switch radio zones, Stratton added.