Here's a warning to parents and teens about the potential spread of sexting photos: Police in Emmaus, Pennsylvania are investigating how nude photos of high school students wound up on an unnamed pornographic Web site.

According to reports, the photos were taken by the teens themselves and shared with classmates. It's not clear right now how the photos wound up on the adult Web site, or how they were discovered. Police believe, however, that the photos were on the site "for some time."

In televised reports, students said that they were aware of the Web site long before parents or authorities. Some said that students were texting links to naked photos of classmates to each other.

The police have not made any statements about the number of students involved, or the number of photos posted to the site. However, an officer associated with the Pennsylvania Internet Crimes Against Children task force said that his office has been inundated with reports of high school and middle school students sharing photos of themselves on cellphones and social networking sites. The superintendent of the Emmaus school district told reporters that kids in several other districts are also involved.

As law enforcement officers regularly point out (and this case illustrates), once a digital photo is shared, it is impossible to limit its spread around the globe or to be sure that all copies have in fact been located and retrieved.

This is not the first time that Emmaus has wrestled with the misuse of electronic devices. In 2009, a 15-year-old Emmaus High School student was charged with posting "upskirt" photos and videos of classmates and teachers online. He was placed on probation and ordered to undergo counseling after pleading guilty in juvenile court.