Montgomery County officials say they have received at least 10 reports of activity related to the scheme from middle schools in recent days and have turned them over to police.
Police are investigating, said Rick Goodale, spokesman for the Montgomery County Police Department.
The episode echoes incidents in Virginia four years ago in which teens faced criminal charges for gathering compromising material and for "sexting."
Montgomery County school officials sent a letter to families at the system's 25 high schools and 40 middle schools Friday evening, alerting them to the problem. They said some Montgomery County students have sent photos, and others have been given the password to the website.
"We want to be preventive," said Derek Turner, spokesman for the district, which is Maryland's largest. "We're hoping to stop kids from engaging and from sending images. We want them to stay safe online."
Turner said little is known about who is behind the effort and whether that person is a student or adult.
"The fact that students are consenting to send their photos is a problem," he said.
Students have come forward at Montgomery schools including A. Mario Loiederman Middle in Silver Spring and William H. Farquhar Middle in Olney.
The issue came to light earlierlast week, Turner said. A letter was sent to Loiederman parents Tuesday.
It remains unclear how many students have received requests for photos on Snapchat or have viewed images on the site, which Turner said includes nude photos with blurred faces.
In the letter to parents, school officials wrote that they have received "multiple reports from community members that one or more individuals is posting inappropriate content on a private social media platform, including nude images of MCPS students. It is our understanding that many of the nude images on the private site were taken by or with the consent of the students appearing in the photos."
In 2014, two teenage boys in Virginia faced charges for collecting compromising photos of more than 50 girls at McLean High School and assembling them in an online file-sharing account.
The teens pleaded guilty in Fairfax County to three misdemeanor charges each for distributing obscene material, as part of a deal with prosecutors. A judge sentenced them to two days each in youth jail and required them to do community service and refrain from using social media and the Internet.
A Manassas City (Virginia) teen was charged earlier that year with child pornography counts for "sexting" an explicit video to his girlfriend. The teen was eventually placed on probation with the stipulation the charges would be dropped if he maintained good behavior for a year.
Montgomery school officials asked parents to call police at 240-773-5400 if their child has information about the site or has been approached through Snapchat for images. School counselors will be available to support students as needed, they said.
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