The 45-year-old man that ran off to Mexico with a 16-year-old Pennsylvania girl has been arrested and the girl has been located by authorities.

Kevin Esterly and Amy Yu were detained Friday in Playa del Carmen, the Allentown police said. An Amber Alert had been issued for the duo by Mexican authorities on Thursday.

'Esterly was placed into custody by Mexican authorities. Amy is unharmed and in good health,' Allentown police said in a statement, according to WFMZ.

Kevin Esterly and Amy Yu were detained Friday, the Allentown police said. An Amber Alert had been issued for the duo by Mexican authorities on Thursday

'Esterly was placed into custody by Mexican authorities. Amy is unharmed and in good health.,' Allentown police said in a statement

'They will be escorted back to the United States to Miami Florida by Homeland Security Investigations agents and United States Marshall Service deputies. Once back in the United States, arrangements will be made to get Amy back to Allentown to be reunited with her mother. Esterly will be turned over to the Miami Police Department and then the extradition process will begin to bring him back to Allentown.'

Esterly will face a charge of interference with the custody of a child.

Mexican authorities on Thursday issued an Amber Alert saying that police believe Amy Yu and Kevin Esterly are in the country, and the teen may be in danger.

The two vanished on March 5, shortly after authorities were notified the pair may have been involved in a romantic relationship. Yu's family previously said the two met at church years ago, and the girl is friends with one of Esterly's daughters.

Bulletin: Mexican authorities on Thursday issued an Amber Alert saying that police believe missing Amy Yu, 16, and Kevin Esterly, 45, are in the country

Yu (left) has not been seen since March 5 when she is believed to have disappeared with Esterly (right), the father of one of her friends, from Allentown, Pennsylvania

School records show Esterly signed Yu out of school 10 times between November 13 and February 9. Police say the teen had changed school documents to list him as her stepfather.

Her mother, Mui Luu, said she feels betrayed. Esterly and Yu had gotten so close she often went on his family's vacations and Esterly had gone to Luu's home for meals.

Luu says she also found text messages suggesting Esterly and her daughter where in a romantic relationship.

'I want to tell her: 'Amy, can you come back to me? I love you. I just hope you come back',' she told CBS News.

Yu's brother, John (pictured), said it seemed Esterly wanted to help his sister. 'We never knew. Now I think he's a very bad guy and Amy's not hanging out with the right person,' he said

The girl had altered her student records to list Esterly as her stepfather, said Gary Hammer, of the Colonial Regional Police

When Yu's mother came to pick her daughter up from school on February 9, the school said her stepfather had already signed her out.

'The mom explained she is a single mother,' Hammer told ABC News. 'There is no stepfather.'

Esterly was subsequently warned to stay away from the teen.

Yu and Esterly were in a 'secretive relationship' which was laid bare in text messages between them which her mother discovered on her phone.

It is not clear if she found them before or after they went missing together.

On March 5, the pair are believed to have left Allentown in a 1999 Red Honda Accord with Pennsylvania plates.

Amy was last seen by her brother, John, who said she fled after being dropped off with him by their mother at their school bus stop.

Esterly had signed Yu out of Lehigh Valley Academy school 10 times between November and February 9 after she changed school records to say he is her stepfather

Esterly and his wife Stacey befriended Yu's family through the church they both attend. She is friends with one of his daughters, seen with him above

Stacey told police that her husband withdrew $4,000 in cash from their accounts before he vanished with Amy on March 5

He told CBS's Meg Oliver he was upset: 'Why would a 45-year-old man and a 16-year-old girl … like, that's disgusting!'

Before fleeing, Esterly withdrew $4,000 from his bank accounts, his wife Stacey told police.

Luu discovered after her daughter vanished that she had taken some of jewelry, her passport and cash.

She said that the family met the Esterly family through church.

Luu discovered after her daughter vanished that she had taken some of jewelry, her passport and cash (Pictured, Esterly with Yu and his children)

Prosecutors have charged Esterly with interference of custody of children. Yu's charter school has also banned him from school grounds since last month (Pictured, Esterly with Yu and his children)

They had them over for dinner at least once and Yu's brother said it seemed the man wanted to help his sister.

'We never knew. Now I think he's a very bad guy and Amy's not hanging out with the right person,' John told WFMZ.

'We need her to come back.'

Prosecutors have charged Esterly with interference of custody of children. Yu's charter school has also banned him from school grounds since last month.