NASHVILLE, Tenn. -- A Channel 4 I-Team investigation has found Tennessee correctional officers were fired and prosecuted for smuggling in cell phones to inmates.

Images: Inmates Photograph Themselves With Smuggled Phones | Video: Prison Guards Deliver Phone To Inmates

The Commissioner for the Tennessee Department of Correction said what the I-Team discovered is an embarrassment.

"Unfortunately, some staff have been compromised," said Commissioner George Little.

While the vast majority of correctional guards never sneak in phones, state records show of all the cases investigated by internal affairs in the past five years, 21 percent of phones were delivered to inmates by correctional officers and other prison staff. Also, those records show that in 50 percent of the cases, the state isn't sure who smuggled in the cell phones; in 29 percent of cases, families and friends were involved.

The I-Team also found that phone smuggling is a problem in private prison companies. Corrections Corporation of America has fired seven correctional officers in the past five years for slipping in cell phones to inmates.

Inmates obtaining illegal cell phones has proven to be deadly in Tennessee. Correctional Officer Frederick Hyatt was strangled to death in 2003 during an escape attempt orchestrated by an illegal cell phone.

In June, police said Metro police Sgt. Mark Chesnut was shot repeatedly by an escaped inmate. Police said that inmate, Joseph Jackson, concocted his escape by obtaining an illegal cell phone behind bars.

Chesnut is now suing the company that owns the prison from which the inmate escaped for $14 million. The lawsuit states Corrections Corporation of America didn't do enough to prevent Jackson from obtaining the cell phone.

"If you introduce a cell phone into a prison, it's no different than introducing a loaded weapon," said David Raybin, Chesnut's attorney. "It is an extraordinarily serious problem."

Photographs obtained by the I-Team show just how brazen some inmates have become in obtaining the cell phones. The photographs show inmates taking pictures of themselves with cell phones while inside their prison cells.

Termination letters of correctional officers and other prison staffers who smuggled in the phones show unique methods of hiding the phones and why some tried to profit off it.

One termination letter showed a prison recreation assistant brought in two cell phones and a large quantity of tobacco inside his leg brace.

One correctional officer brought in a brand-new cell phone that had never been activated.

Another officer said he made a bad choice when he brought in a cell phone battery and a SIM card, intending to give it to an inmate for $160.

Little said the low pay of correctional officers is a problem and that the temptation is real.

"A cell phone right now coming in can be an extra $300 for an employee," Little said.

Raybin, who has spent years in Tennessee prisons helping to write the state's criminal code, said oftentimes guards perceive giving an inmate a phone as harmless.

State correction officials have opted to prosecute former employees who smuggled in cell phones. In two recent cases, two correctional officers pleaded guilty to introducing contraband into a penal facility and received 11 months probation.