![amy yu_kevin esterly](https://a57.foxnews.com/static.foxnews.com/foxnews.com/content/uploads/2018/09/1200/675/amy20yu_kevin20esterly.jpg?ve=1&tl=1)
Police believe Amy Yu “willingly” flew from Philadelphia International Airport to Dallas, and ultimately to Cancun, Mexico, with Kevin Esterly. (Allentown Police Department)
A 45-year-old man and a 16-year-old girl who were last seen on Monday may be traveling together and have a "secretive relationship," officials said.
The Allentown Police Department said in a Facebook post that Kevin Esterly and Amy Yu "could possibly be endangered," and may be traveling in a 1999 Red Honda Accord with Pennsylvania tags KLT-0529.
Yu is described by police as an Asian female, standing 4’11”, and weighing approximately 90 pounds, while Esterly is described as being as being 5'9'' in height and weighing 185 pounds.
Esterly had signed out Yu from a charter school 10 times between November 2017 and February, and investigators said the pair have a "secretive relationship," according to court documents obtained by The Morning Call.
Yu's parents had contacted authorities on Feb. 9 after they found out he signed their daughter out of school without permission, the records stated.
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Her mother reported her as a runaway on Monday, and she is believed to have seen with Esterly around 7:09 a.m. Yu's mother reported that personal documents and jewelry had been taken from her home, the Morning Call reported.
When authorities contacted Esterly's wife, they discovered he had withdrawn $4,000 from her bank account and taken personal documents.
Authorities advise that anyone who sees them or may have information should call Allentown police immediately.