Pennsylvania State Police said the case involves a 15-year-old boy and a 14-year-old girl.
No charges have been filed so far. Police say they are trying to determine if the exchange of those explicit photos between two consenting minors amounts to a crime.
Investigators say the teens sent the photos between 7:30 a.m. and 2:00 p.m. on Thursday.
Polie didn't specify whether the photos were sent by text message or were emailed, but police do alleged the exchange happened during school hours.
Officials from the East Penn School District dispute that, saying "As far as we are aware, this was an out of school event being handled by police."
Students at Emmaus High School, who are just back from spring break, say this story remains the hot topic in class.
"When I was sitting in homeroom today and we were talking about it, we were saying that kids our age don't really care that much. But, for parents - and their parents especially - it's probably a huge deal," said Laura Capehart.
All this comes about a year-and-a-half after another texting scandal involving Emmaus High School students. In that case, some teenage boys posted previously-taken nude pictures of their ex-girlfriends on an X-rated website.
Fellow students say even though they are often warned about the potential long-term consequences of inappropriate photos and comments, it seems to go over some teenagers' heads.
"I don't think they realize that when you send something it's out there forever and that it's really easy to get access it," said student Alex Nader.
"Somebody sends a picture then it pops up four years later for a job interview, then you're not getting a job or not getting accepted into a college," said student Matthew Kline. "I mean, I don't understand why people do it."