The controversy has roiled the Cañon City High School, about 115 miles south of Denver, and police are also investigating if any underage students were coerced into the lewd photography and whether any adults were involved, the school said in a statement.
"It has come to the attention of the Cañon City School District that a number of our students have engaged in behavior where they take and pass along pictures of themselves that expose private parts of their bodies or their undergarments," school officials said in a statement on Facebook.
Charges could amount to a Class 3 felony if students took "a picture of themselves showing a naked private body part and sent it to another person, ... received such a picture and forwarded it to another person, or ... received such a picture and retained possession of it over time," the Cañon City School District said.
"We will be identifying people in the images," he added. "We're haven't interviewed anybody yet. We're in the process of obtaining search warrants. We're in the process of coordinating forensic investigations of cell phones."
Nude photos taken on campus
Some of the nude photos are believed to have been taken on campus, said Schools Superintendent George Welsh.
Students have been suspended, but the number wasn't disclosed, according to the schools chief.
"There isn't a school in the United States probably at this point that hasn't at some point dealt with the issue of sexting," Welsh said.
Students used a photo vault app that hides the nude photos by appearing to be a calculator or media player, Welsh said.
"When you go into it and you ... hold a certain button long enough, a prompt for password comes up. Once you enter that password, then any messages that have been sent from photo vault to photo vault start coming up," Welsh said.
The app is "a little bit like Snapchat," he added. "You can choose for the photo not to be able to remain on the device."
Questions about sex offender registration
Fremont County District Attorney Thom LeDoux encouraged students to surrender phones and digital devices with the nude photos.
"For parents that may be having conversations with their children or reviewing cell phones as the superintendent recommended, they need to understand that continuing or ongoing possession of these materials does constitute a very serious crime for the adults and for the children," the prosecutor said.
Any convictions could involve registration as a sex offender, the prosecutor said.
"We take the implications of requiring to register someone as a sex offender very seriously, and we would only seek to have that application of the law to these circumstances if we felt that it was absolutely necessary," LeDoux said.
"It is not necessary that all of the children involved in the circumstance will have to register as a sex offender. We will only seek that remedy through the courts if we believe there is no other choice and is in the best interest in the victim involved and the children involved in our community," the prosecutor said.
Tipster called youth hotline
Already, "a large number" of the school's football players have been implicated in the accusations, leading coaches and administrators to conclude that "stepping on the field to play this weekend to represent the Cañon City community is just not an option," the school statement said.
"We realize this decision will unfairly penalize many of our fine young men who clearly did not participate in these actions," the school district said.
The police investigation began this past week after anonymous tipsters called Colorado's Safe2Tell hotline,
which allows young people to report threatening behavior in a way that keeps them anonymous and safe, school officials said. The district also received students' reports about the sexting.
The district is now developing a plan to further educate students on "the 21st Century skill that all citizens use technology in a legal and ethical fashion," officials said.
Lisa Graham, 46, said her daughter was a freshman at Cañon City High School two years ago when male students sent her unsolicited nude pictures over Snapchat and by text message.
Graham said her daughter told her she was also "propositioned" for her own nude photos, though she never sent them.
"We talked about it and that was really the last I ever heard of it," Graham said.
She said she was supportive of the superintendent and the school's response to the scandal but concerned that action had not been taken sooner.
Graham said at a meeting earlier in the week the district superintendent warned parents about the photo vault apps used by the students to conceal the illicit photos and said that the school would "work on educating the children on proper social media."
Parents were encouraged to talk directly with their children about sexting, school officials said.
"No matter what the police investigation uncovers, the Cañon City School District will hold its students accountable for their actions as outlined in district policies relating to cyber bullying, sexual harassment, and irresponsible behavior," the district said.
Recent studies shows that teens sending nude photos via text -- or sexting -- is more common
than parents might realize or want to admit.