OTTAWA -- Ottawa police say a 56-year-old public school teacher is facing sexual assault charges in connection to alleged incidents involving a teenage girl between 2015 and 2018.

The Ottawa Carleton District School Board says it contacted police after staff were made aware of allegations against the teacher three years ago.

"The investigation revealed that incidents occurred while the man was in the course of his duties as a teacher between 2015 to 2018, while employed by the Ottawa Carleton District School Board, and involved a teenage girl under 18 years of age," said Ottawa police in a statement.

Darren Green, 56, of Ottawa is charged with two counts of sexual assault, one count of sexual interference and one count of sexual exploitation.

In a statement to CTV News Ottawa, the Ottawa Carleton District School Board said Green was removed from the classroom when staff were first made aware of the allegations.

"The OCDSB has been cooperating fully with the Ottawa Police Service since the start of this investigation. We contacted authorities after we were first made aware of concerning allegations in 2018," said the board.

"The employee was immediately removed from the classroom at that time, and has not returned. This will continue until the conclusion of this matter through the courts."

The board says it will contact the Ontario College of Teachers and conduct an internal investigation.

Ottawa police said Thursday that investigators are concerned there may be more victims.

Anyone with information is asked to contact the Ottawa Police Service Sexual Assault and Child Abuse Unit at 613-236-1222, ext. 5944.