A looped clip of a Hitler speech broadcast on an Austrian train shocked and frightened passengers Sunday.

The recording of some 30 seconds of the German leader ranting and people shouting the Nazi salute “Sieg Heil!” several times started playing shortly before the train reached Vienna.

David Stoegmueller, a Green Party MP who was in one of the compartments, told the BBC that the same recording was played twice, with train operators unable to stop it or make announcements while it played.

He added that a fellow passenger emailed him that a concentration camp survivor cried when she heard the voices play loudly throughout the train.

Rabbi Schlomo Hofmeister, the chief rabbi of Vienna, was also on the train. He told CNN on Monday that initially there was “strange music, snippets of conversation and laughter which suddenly turned into a Hitler speech played louder and louder.” At first he thought it was an error, then a terrible joke, but then he “felt queasy” because the thought occurred to him that the train had been hijacked, he said.

Some people panicked while others laughed, he added.

What was mostly “disturbing,” he wrote on Twitter following the incident, was that those in charge on the train “didn’t provide any explanation or reassurance,” simply “ignoring” what had happened.

A third passenger, journalist Colette Schmidt, echoed the rabbi’s anger and fright, telling CNN that “no conductor, no one came, there was no one to see. We were alone with this madness. ‘Who is driving this train now?’ I asked myself…. It was very, very scary.”

“Quite apart from the fact that I and other Austrians were completely shocked: what does a guest from abroad think when Hitler speeches are played over loudspeakers in our trains? Supposedly it came from ‘the technology.’ What?!” Schmidt tweeted.

“We clearly distance ourselves from the content,” the train’s operator, Austrian Federal Railways (ÖBB), said in a statement sent to the BBC. “We can currently assume that the announcements were made by people directly on the train via intercoms. We have reported the matter to the police.”

The authorities later arrested two people, identified through the train’s surveillance cameras, for apparently opening the intercom with a duplicate key to play the recording.

“It is absolutely clear that any abuse should be punished, especially the illegal use of Nazi symbols is absolutely unacceptable,” an ÖBB spokesperson told CNN.

The National Socialism Prohibition Act of 1947 mandates prison sentences for those attempting to revive or glorify Nazism. Depending on the crime, a person could serve up to 20 years in prison.

Image - Shutterstock