A high school nurse's aide was arrested after police said evidence surfaced that she had an inappropriate relationship with a student.

Maria Calvillo, 38, has been charged with having an improper relationship with a student.

According to an affidavit, Alief Independent School District Police said the 17-year-old student's mother discovered sexually explicit Facebook and text messages between the high school senior and the nurse's aide in October 2012.

Calvillo initially denied having sex with the student, but police said she later admitted they did have sex on two separate occasions -- both times in a storage closet in the nurse's clinic.

The student was then interviewed and admitted to the relationship, detectives said.

School district officials said Calvillo was hired about a year ago and was placed on administrative leave after the district learned of the allegations. She was fired on Nov. 5 for violating the district's code of ethics, school district officials said.

"The district takes any allegation of this nature very seriously and has been cooperating fully with the Alief ISD Police Department and the Harris County District Attorney's Office throughout the investigation," a statement from the school district read.