A federal prosecutor who authorities say came to Michigan expecting to have a sexual encounter with a 5-year-old girl has been indicted on an additional charge and ordered held without bail.

John D.R. Atchison, 53, of Gulf Breeze, Fla., an assistant U.S. attorney based in Pensacola, Fla., was arrested Sunday at Detroit Metropolitan Airport when he arrived for a meeting with a woman he thought was going to let him have sex with her young daughter, authorities said. The woman actually was a Macomb County sheriff's detective and part of an Internet sex sting operation.

He initially faced charges of use of the Internet to seek illicit sex, which carries a mandatory minimum of 10 years in prison and a maximum of 30 years, and interstate travel to engage in illicit sexual contact, which carries up to 30 years.

On Tuesday, a federal grand jury added a charge of crossing state lines with intent to have sex with someone under 12, which carries a minimum 30-year prison sentence and a maximum of life.

Defense lawyer James Thomas declined to comment after a hearing Tuesday before U.S. Magistrate Virginia M. Morgan, who denied bail.

Atchison's boss, U.S. Attorney Gregory R. Miller, said in a statement Tuesday that his staff was cooperating with the FBI, federal prosecutors and Michigan investigators. The status of Atchison's employment was unclear.

Atchison is president of the Gulf Breeze Sports Association, which runs youth baseball, softball, cheer leading, soccer, football and basketball programs. The group said Tuesday it was placing him on leave until the charges were resolved.

According to an FBI affidavit, Atchison exchanged instant messages with Macomb County sheriff's Detective Linda Findlay, who is part of the 6-year-old Macomb Area Computer Enforcement Team.

"Findlay created an online undercover persona ... of a mother with minor children who is interested in allowing men to have sex with her children," FBI Agent Matthew A. Bowman wrote.

When he arrived Sunday, he was carrying presents for the girl, including a doll and earrings, and also had sexual materials, Sheriff Mark Hackel said.