The photo was posted online in late 2012 or early 2013.
School officials heard about the photo a few months ago and called Edmonds police, who launched an investigation.
Detectives now are wrapping up their case.
The young men are suspected of sexual exploitation of a minor, a felony, Edmonds police Sgt. Mark Marsh said.
Police allege that two of the boys, who were 17 and 18 when the incident was reported, were having sex with the girl when one of them took a picture.
The picture was shared with a friend, with instructions to delete it after viewing it, Marsh said. Instead, the friend posted the photo to the Internet.
The photo later was deleted, but "the damage was done," Marsh said.
"To take a picture of a minor in a compromising sexual manner, and letting that out, is a felony, and the separate (issue) would be the young man who posted the picture on the Internet would be in itself a crime," he said.
The Herald is not naming the young men because they have not been charged.
All three have cooperated with the investigation, Marsh said.
"We don't think there's a risk of any further victims or of them repeating this type of behavior," Marsh said.
The case will be forwarded to Snohomish County prosecutors for review.
When the incident was reported, two of the young men and the victim attended Edmonds-Woodway High School. The other young man is from Shoreline.
Earlier this year, Edmonds school officials said the alleged incidents took place off school grounds and not during school hours.
They said the district took some "disciplinary actions" but did not elaborate.
Rikki King: 425-339-3449; firstname.lastname@example.org
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