WATERLOO (AP) — The parents of two missing Iowa cousins have prepared an open letter to whoever abducted the girls, asking for the children to be freed.

It’s been four months since 11-year-old Lyric Cook and 9-year-old Elizabeth Collins were last seen riding their bicycles near a lake in Evansdale. The girls have had birthdays since then. Authorities believe the girls were abducted.

The parents submitted their letter to the Waterloo-Cedar Falls Courier. The Courier reported Heather Collins composed the letter, which was then signed by her husband Drew Collins and Lyric’s parents, Daniel Morrissey and Misty Morrissey.