LOS ANGELES -- A federal child pornography investigation is underway after someone apparently stole a picture of Jamie Lynn Spears breast feeding her baby girl, TMZ is reporting.

The picture was reportedly one of 12 showing Britney Spears, Jamie Lynn, daughter Maddie and the baby's father Casey Aldridge. Jamie Lynn's left breast is exposed in the breast feeding picture, according to TMZ.

Aldridge took his digital camera to a local Wal-Mart in Louisiana to have copies made, the website reported. It's believed a Wal-Mart employee may have made extra copies and tried selling them.

Because Jamie Lynn is a minor, selling the pictures -- or buying them -- could constitute a violation of federal laws prohibiting child pornography.

Other pictures in the set, according to TMZ, include Britney holding the baby, one of Jamie Lynn, Britney, Brian (Britney's brother), Lynne Spears and Jamie Spears around Jamie Lynn's hospital bed, some of Maddie by herself and one of Jamie Lynn in a negligee holding the baby.

According to TMZ, authorities are trying to find the man who is attempting to sell the photos and Britney's lawyers are considering going after Wal-Mart for the alleged security breach.