Authorities say the unidentified man and woman are seen molesting a girl in the widely circulated images seen in many collections.
"We need the public's help in identifying the man and woman responsible for molesting this young girl, whose victimization has continued with the trading of these images by those who collect child pornography," said U.S. Attorney Andre Birotte Jr. in a statement.
At a news conference in Downtown L.A., federal investigators outlined their case against the unidentified couple referred to as John and Jane Doe. The photographs first turned up in Chicago in 2007 in an unrelated child pornography investigation. Ever since, federal investigators have been trying track down the man and woman responsible for the heinous crime.
The girl appears to be about 13 in the pictures. The male suspect's face has been purposely obscured in the images, but the female suspect's face can be seen.
The female suspect has several tattoos, including a black tattoo on her right hip resembling a butterfly, a tattoo of a curled up cat on her right shoulder blade, a tattoo with words across the top of her left wrist and a tattoo on the upper portion of her left breast.
Investigators believe the photos were taken about 11 years ago at an apartment in the San Fernando Valley. They base that theory on several items in the background of the photos, including a calendar.
Anyone with information or tips is urged to call (866) DHS-2ICE or visit http://www.ice.gov/exec/forms/hsi-tips/tips.asp. Tips may be reported anonymously.