Missing teen girl, 45-year-old man believed to be in Mexico

An Amber Alert was issued in Mexico on Thursday night for a Pennsylvania teen who went missing with a 45-year-old man last month.

The Twitter alert indicated that 16-year-old Amy Yu and Kevin Esterly have left the U.S., and that Amy might be in danger.

The Lehigh Valley Academy Charter School student and Esterly were in a "secret relationship" when they vanished on Feb. 9, according to investigators.

Esterly had signed the teen out of school 10 times during a three-month stretch without her parents' permission, including the day they disappeared. Amy had modified school documents to list him as her stepfather.

"We can confirm that Mr. Esterly was last present on school grounds on February 9, 2018," Lehigh Valley Academy CEO Susan Mauser previously said in a statement, according to NBC in Philadelphia. "After that date, due to circumstances we cannot disclose pursuant to student privacy constraints, he was prohibited from entering school grounds, and the police were to be notified if he returned."

The teen's family previously said the two of them met at church years ago, and Amy is friends with one of Esterly's daughters.

"That’s why we’re working this hard," Allentown Assistant Police Chief William Reinik told CBS in Philadelphia. "We have a family who has a 16-year-old girl, no matter why she left the area. We have this family who still doesn’t have answers."

Amy's mother Miu Luu made a plea for her daughter's safe return to CBS News earlier this month.

"I want to tell her — Amy, can you come back to me? I love you. I just hope you come back," she said.

Esterly might be driving a two-door red Honda Accord with a KLT-0529 license plate, according to NBC. Anyone with information on their whereabouts should contact the Allentown Police Department at (610) 437-7751.

With News Wire Services