HAMMOND, Ind. (CBS) — The fired pastor of a megachurch in Hammond, Ind., has signed a plea deal in federal court, admitting he took a 17-year-old girl across state lines for sex.

Dr. Jack Schaap – who was fired as pastor of First Baptist Church of Hammond in July – will make an initial appearance at the federal courthouse in Hammond at 3 p.m. Wednesday, before U.S. Magistrate Judge Paul Cherry. Schaap is charged with interstate transportation of a minor with intent to engage in criminal sexual activity.

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Schaap, 54, was fired in late July after admitting to church leaders that he had a sexual relationship with a 17-year-old girl who is a member of the church. Church members were informed of the investigation into the case last month, just days after Schaap was removed from his post.

Terry Duff, chairman of the church’s Board of Deacons said last month that he was informed of the conduct in late July, then met with the board of deacons two or three times before confronting Schaap about the allegations. Duff said Schaap, who is married to the daughter of the church’s founder, admitted having a sexual relationship with a 17-year-old girl.

The board voted to dismiss Schaap on July 30 and announced the dismissal the next day.

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“He had an inappropriate relationship with a minor,” Duff said.

Asked if he is concerned Schaap might have had inappropriate relationships with other young members of the church, Duff said, “We have no idea at this time. That’s why we’re asking anybody, anybody who has information to please come forward and let us know.”

Schaap had been pastor at First Baptist for 11 years, and had grown the church to 40,000 members worldwide.

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The church is a conglomerate that includes a 7,500 seat auditorium and is headquartered in the old federal courthouse in Hammond, IN. Schaap helped grow the church into its ‘mega’ status with 15,000 people attending weekend services.