By Christina Maxouris, Eric Levenson and Artemis Moshtaghian, CNN

(CNN) -- A photo showing a group of male, mostly white Wisconsin high school students with their arms raised in what appear to be Nazi salutes has sparked an investigation by police and the school district, along with criticism from a Holocaust memorial group.

The image of students in the Baraboo School District originally was posted on the @GoBaraboo parody account with the caption, "We even got the black kid to throw it up."

The picture, which was tagged #Barabooproud, has since been taken down, and police and school officials now promise to look into it further.

The photo, in which students appear to "be making extremely inappropriate gestures," dates to last spring and was not taken on school property or at a school-sponsored event, District Superintendent Lori Mueller said Monday in a statement.

The district is "extremely troubled by the image," which shows the teens attired for prom, and is working with local authorities to investigate how and why the photo was taken, Mueller said in a letter sent Monday afternoon to parents.

"The school district is investigating this situation and is working with parents, staff and local authorities," Mueller said in the statement. "If the gesture is what it appears to be, the district will pursue any and all available and appropriate actions, including legal, to address the issue."

"Clearly, we have a lot of work to do to ensure that our schools remain positive and safe environments for all students, staff and community," she added in the letter.

Baraboo police tweeted that they are assisting the district's investigation since being made aware of a "controversial photo of a group of high school students."

Not everyone in the photo is participating in the gesture. Jordan Blue, a student in the top right of the image whose hands are not raised, told CNN the photo was taken as students gathered at a local courthouse for professional prom photos.

"The photographer said to raise your hand, but he didn't say a specific way, and my peers should not have raised it in the specific way that was the offensive way and hurtful way," Blue said.

Blue said the gesture made him uncomfortable and scared.

"It was a scary moment, and it was very shocking and upsetting, and it was a huge misrepresentation of the school district and the community of Baraboo," he said.

About 40 miles northwest of Madison, the Baraboo School District had just more than 3,000 students, with a 17.6% minority population, in the 2015-16 school year, its most recent available statistics show.

Holocaust group and ACLU criticize photo

The Auschwitz Memorial Twitter page was among groups that have criticized the photo, with its smiling, well-dressed teenagers apparently making a gesture of hate.

"This is why every single day we work to educate," the organization posted. "We need to explain what is the danger of hateful ideology rising. Auschwitz with its gas chambers was at the very end of the long process of normalizing and accommodating hatred."

The group also attached a link to its website, offering lessons on the history of Auschwitz.

"If @barabooSD wishes to know more about what can be the extreme result of normalization of hatred -- and hatred is enrolled in this symbol -- please see some online lessons dedicated to the history of Auschwitz," the group tweeted.

While "students have First Amendment rights," the American Civil Liberties Union of Wisconsin criticized the "shocking and reprehensible" way these students appear to have exercised those rights.

"We hope these students understand what a mistake this was, and we hope that they will join work against the hateful ideology that they appeared to treat so casually in the photo," the group wrote Monday.

"It is equally critical for schools to foster an environment that is safe, welcoming, and non-discriminatory for other students," the ACLU wrote. "To that end, we urge the Baraboo school district to not only investigate this situation but to bring in experts in anti-bias training to engage with students and faculty."

The photography agency that took photos of the Baraboo High School students, Wheel Memories, originally posted thumbnails of several photos from the shoot, including the one in question.

The photos have since been removed, the agency wrote on its site in a message that blames "jerks" and online negativity.

"It is too bad that there are those in society who can and do take the time to be jerks; knowingly and willingly to be jerks! The internet can be a wonderful tool but for some there is an overwhelming urge to destroy. The destruction may not be physical but instead it can be bullying that is intellectual or emotional," the photo agency wrote.

"To anyone that was hurt I sincerely apologize. To those who have harmed them, we as society often ignore them I have chosen not to do that. YOU ARE JERKS! Grow up! Be kind, Be gentle, Be civil!"

CNN has reached out to several students in the photo, as identified through social media, and has also reached out to the photographer for comment.