A N.J. Department of Corrections teacher has been fired and arrested after prison officials discovered her extensive affair with an inmate.

Chong-Hwa Chang taught in Trenton, N.J. at the New Jersey State Prison. NJ.com reports that the 42-year-old was arrested on Jan. 29. She's been charged with one count of sexual assault. The Department of Corrections investigated Chang and discovered she'd been intimate with an unnamed inmate more than 20 times. In that time, the teacher, who earned $73,000 per year, gave birth to two children.

The Mercer County Prosecutor's Office authorized the Department of Corrections to search Chang's home and car, according to the Associated Press. They found shocking evidence of the alleged crime.

Chang reportedly kept a diary. In it, she admitted to at least 20 sexual encounters with the inmate and detailed her pregnancies. The investigators also found explicit photos, according to NJ.com.

The teacher has been employed with the Department of Corrections for nine years, according to NJ.com. It is unclear if the crime was committed over the course of the nine years or during a specific time period.

Chang's being held on $50,000 bond and has been terminated from her job.

Unfortunately, this isn't an isolated case of prison staff sexually abusing inmates.

The Bureau of Justice Statistics found that between 2011 and 2012, 3.2 percent of all people in jail were allegedly abused in their correctional facility.