A former sixth-grade teacher at a Simi Valley, Calif., elementary school turned herself in to police Tuesday after being accused of committing sex crimes on a student under the age of 14.

Malia Brooks, 32, was booked on suspicion of five sex-related counts. Authorities would not divulge the age of the victim or whether he was a student in Brook's class, although NBC Los Angeles reported that he was a student at the school, which serves children in kindergarten through sixth grade.

Officials said the relationship began in late 2012 and lasted four months, according to CBS Los Angeles.

Investigation of Brooks began in February 2013, after Simi Valley Unified School District officials learned of alleged inappropriate conduct between the teacher and a student. Brooks was placed on administrative leave during the investigation, and resigned June 5.

In court Wednesday, Brooks pleaded not guilty to charges of lewd acts on a child, oral copulation of a person under 14 years of age and three counts of genital penetration by a foreign object, according to CBS Los Angeles.

Brooks' attorney said his client suffers from mental illness.

"We've had her diagnosed and she's in treatment," Bamieh told NBC Los Angeles. "My guess is a lot of the charges precipitated from that illness."

According to KTLA, Brooks, who had worked at the school district since 2004, was once married with two children, but is now divorced.

In a statement obtained Wednesday by NBC, school district Superintendent Kathy Scroggin said that Brooks had "been evaluated until now as an exemplary teacher" and reassured parents that "the district has taken every precaution to ensure the safety of students."