STORM LAKE, Iowa -- Authorities say three teenage girls have been charged with sending nude pictures of themselves to an Iowa man who's been charged for possessing the photos.

The girls are ages 16 and 17 and have been charged as adults with felony exploitation of a minor. Online court records say 19-year-old Alex Case is charged with sexual exploitation of a minor.

Buena Vista County Sheriff Gary Launderville says that under Iowa law, it's a felony to send such images and a misdemeanor to possess them. Launderville says that makes the girls both victims and defendants.

He says he doesn't know how Case became acquainted with the girls.

A public phone listing for Case could not be found. Online court records don't list the name of his attorney.