GREENEVILLE, Tenn. (WVLT) -- The man investigators have called the "top suspect" in the disappearance of Megan Maxwell, 19, in Cocke County pleaded guilty to unrelated federal charges in U.S. District Court Monday.

Jeffery Lee Stock, 41, of Del Rio, pleaded guilty to violating federal sex offender registry laws.

"Stock faces a maximum term of ten years in prison, a maximum fine of $250,000, a maximum term of supervised release of life, and a special mandatory assessment of $100," according to a release from U.S. Attorney James R. Dedrick's office. "He remains in federal custody pending sentencing.

Dedrick's office says Stock was convicted on two counts of sexual battery in 1998 in Indiana, where he's originally from, before leaving the state for Tennessee in August 2008 without notifying law officers in either state, as required by sex offender registry laws.

He was picked up by Knoxville Police on Oct. 9, 2008 on drug charges. He registered with the Tennessee Bureau of Investigation as a sex offender at that time, according to the release.

Megan Maxwell disappeared on April 26, 2009. Her burning 2001 Mitsubishi Eclipse on US Hwy. 25/70.