A University of Minnesota associate professor engaged in a lurid Internet exchange with a 15-year-old girl from Louisiana, coaxing her to take photos of herself naked and to send them to him, according to FBI documents filed in U.S. District Court this week.

During the inquiry, launched after the girl's mother contacted authorities, an FBI agent posed as the girl online and conducted further online exchanges with the professor. He was arrested 12 days ago at his southeast Minneapolis home.

On Monday, U.S. Magistrate Judge Tony Leung ordered that Woody Dale Branton, 62, an associate professor of neuroscience at the U, be held without bail and transferred to Louisiana for court proceedings.

Leung determined that there was probable cause that Branton had attempted production of or produced child pornography and had enticed a minor to engage in sexually explicit conduct.

Minneapolis FBI agent Maureen T. Lese filed an affidavit saying the girl's mother discovered the sexual exchanges and filed a complaint with Union Parish's Sheriff's Office in Louisiana. She alleged that her daughter had been conducting sexually explicit conversations with Branton through Facebook's instant-messaging system, including sending him photographs of herself naked.

Lese wrote that the girl's mother had known Branton since high school, when they were close friends. As adults, they reconnected through Facebook, and Branton subsequently became a Facebook friend of her daughter.

During the exchanges with the girl, Lese wrote, Branton allegedly sent the girl a "sexual device."

In early December, after learning of the communications, the mother confronted Branton before calling law enforcement. She then began working with the FBI in its investigation of Branton.

FBI agent Jared Medaries of Louisiana, posing as the 15-year-old, created a Facebook account and resumed the sexually explicit conversations with Branton.

At a hearing last Wednesday, FBI agent Robert Blackmore argued that the charges were serious enough to carry a 15-year sentence and that releasing Branton would allow the offenses to continue. Leung rejected a defense request that Branton be given the less restrictive option of home monitoring.

Steve Henneberry, a spokesman for the University of Minnesota, said Branton was hired by the university in 1988. "His status is currently under review," Henneberry wrote in an e-mail. "He was not scheduled to teach any classes this semester."

The federal public defender's office, listed in court records as representing Branton, did not return a phone call or e-mail.