A 28-year-old woman who works as an occasional supply teacher with the York Catholic District School Board has been charged with the sexual assault of a teenage student.

York Regional Police said they began investigating after receiving information about a teacher alleged to have been involved in a sexual relationship with a male student between October and December of last year.

The suspect has been working as a supply teacher with the YCDSB since 2014, police said.

In a statement, the school board said the teacher is on leave as police investigate.

“These allegations are certainly upsetting for YCDSB,” board spokesperson Sonia Gallo said in a statement. “We take very seriously our responsibility to ensure a safe and respectful working and learning environment for all our students and staff.

Gallo said the teacher “was immediately removed from her teaching assignment” after the allegations came to light.

The statement added that board psychologists and chaplains will be available to support students and staff who have concerns.

Marianna Riossi of Vaughan has been charged with three counts of sexual assault and three counts of sexual exploitation.

She is scheduled to make a court appearance in Newmarket on May 6.

Investigators said they want to ensure there are no further victims and are asking anyone with information to come forward.

The allegations have not been proven in court.