A female teacher at a private Burnaby Catholic school who is under police investigation for having a sexual relationship with a Grade 11 student has denied the allegation, according to the school's principal.

"The teacher was very distraught — very, very distraught — and she denied it," said Darrell Hall, the principal of Burnaby's Saint Thomas More Collegiate.

Late last month, two students told Hall they believed the teacher had an inappropriate relationship with one of their classmates last year, he told CBC News on Thursday.

"They came into my office late one day and they revealed the allegation and as soon as we heard the allegation, we got the police involved, talked to the teacher and the matter is now in the hands of police," said Hall.

"My main concern was the safety of our students and that's why we acted very quickly in turning this over to police," said Hall.

The teacher immediately took a personal leave, but she has an untainted record in her four years at the school, Hall said

"She was always a very popular teacher with students and staff and there's no blemish on her record anywhere," he said.

The alleged victim, whose name has not been released, is now in Grade 12 and still attends the school.

Burnaby RCMP Cpl. Alexandra Mulvihill said the RCMP's child abuse and sexual offence unit is now investigating.

"As this is early on, we can't really get into, or nor do we know, how serious this is, in regards to the relationship that may have existed. Obviously we take these allegations seriously and we will investigate them to their full potential," said Mulvihill.

Saint Thomas More Collegiate teaches students from Grade 8 to 12.