A Jew was arrested in Auschwitz Birkenau because kids in a group he was leading were singnig the "Ani Maamin" song.

I don't know what the crime was that they committed - perhaps disturbing the peace?

From INN:

Guards at the Auschwitz Birkenau concentration camp memorial site shouted at Jews who sang “Ani Maamin” – a song based on lines from Rambam (Maimonides) which was known as the Hymn of the Camps – during a visit to the camp and fined their guide 1,000 zloty, or about $350.
So says the guide, Rabbi Rafi Ostroff, who is also the head of the Etzion Bloc Religious Council. 

Ani Ma'amin has several tunes, one of which was composed by a Hassidic rabbi in the cattle cars en route to the Nazi concentration camps. The song was then adopted by other Jewish prisoners and became known as the Hymn of the Camps
“Dear friends,” wrote Rabbi Ostroff on Facebook. “Friday-yesterday. I am leading a group of Bnei Akiva from Australia and South Africa. As usual the group sings holy songs of prayer during the visit. This time the guards of the camp hounded us all the time, shouting at us not to sing. Even in the gas chamber of Aushwitz 1, the guard came up to me and shouted at me: 'tell them immediately to shut up'.
"We then went to Birkenau. In a secluded part of the camp the boys spontaneously started singing 'Ani Maamin'. This was the song that prisoners sang on the way to be murdered there. A guard drove after us with his car and demanded that they be silent. I told him that I don't have control over this as they are singing from their hearts. He then threatened to arrest me and called the police.
"In my group were a few boys [whose] grandparents were prisoners or were murdered in Auschwitz. We cried a lot on that day when they shared their stories with us. I was threatened with 24 hours imprisonment or paying a 1000 zloty fine (about $350). I opted to pay as it was 2 hours before Shabbat.
"It is totally unacceptable that the camp administration treats Jewish groups as if we are tourists to the site like any other group. They have to be considerate and compassionate to Jewish groups. We are not visiting there out of curiosity. It is a journey to the depths of our souls.
"If the camp administration does not understand this, then they are incompetent to rule of this sacred site. The next rule will be that we are not allowed to carry Israeli flags as it might offend someone… I demand a formal apology from the camp administration and the refund of the fine that I had to pay.”
Program Coordinator for the Bnei Akiva trip, Michael Rainsbury, gave his own version of events:
“My account of an incident that took place at Auschwitz-Birkenau on Friday with Rav Rafi Ostroff on the World Bnei Akiva Hachsharat MTA Boys trip to Poland:
“After the tour of the site, we marched out, singing 'Ani Ma'amin' with pride and waving our Israeli flags. Unfortunately, at this point as well as twice previously in Auschwitz I, we were ordered not to sing by the security personnel at Birkenau despite it being an established practice for Jewish groups. The group felt a strong sense of pride and duty to sing the same song Jews sang on the way to their deaths and continued to sing. Security refused to let the matter go and persisted in stopping us singing, despite us calmly explaining to them our reasons for doing so. They then called the police, who arrested our guide, Rav Rafi Ostroff, for breaking the rules of the site. Rather than being in custody for Shabbat, we paid a fine and left for Shabbat. At all times throughout the situation, we kept the group removed from the incident and no one was placed in a dangerous situation. To their credit, they remained dignified throughout the incident, merely continuing to sing with pride. We have already started making representations to ensure that we receive our money back, the site apologise for the behaviour of their staff and that this will not happen to another Jewish group again.”