ALLENTOWN, Pa. (AP) - A 45-year-old man who signed out a 16-year-old girl from her Pennsylvania school 10 times in the last few months before the two went missing was able to do so because she had changed school documents to list him as her stepfather.

  

Allentown police issued a missing person alert Wednesday for Kevin Esterly and Amy Yu. Police also issued a warrant for Esterly's arrest alleging interference with the custody of a child.

  

Gary Hammer, of the Colonial Regional Police, tells ABC News the girl's mother arrived to pick her up last month and school workers said she'd left with her stepfather. The shocked woman is a single mother.

  

Amy's younger brother and mother tell WFMZ-TV the two families met at church and Amy is friends with one of Esterly's daughters.