An ex-inmate was arrested at California's New Folsom Prison after he was caught sneaking back onto the prison grounds nearly two years after his release.

Marvin Lane Ussery, 48, was paroled in 2009 after serving time for a robbery charge at the prison in Sacramento, Calif., Fox40.com reports.

Ussery reportedly returned to the prison grounds some time overnight Wednesday, and officers spotted him using thermal imaging equipment.

Officials aren't sure why Ussery returned to the prison, but they admit there has been a growing trend of former inmates sneaking onto the grounds to leave contraband items for other inmates to retrieve later.

Correctional officers have searched inside the prison for any trace of contraband, but at this time there is no evidence to suggest Ussery left contraband items on the grounds.

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