Toronto police have opened an official investigation after the administrators of a Canadian sperm bank have accused a former employee of replacing hundreds of sperm donors’ specimens with his own.

Robert Casgrain, 58, who has worked as a janitor at the Toronto-based fertility clinic since 1996, is suspected by administrators of switching hundreds of semen specimens with his own sperm over a 20 year period.

Administrators claim in the official police report that they estimate Casgrain could potentially be the father to over 22,000 children over a period stretching two decades.

Although Robert Casgrain’s motives for replacing the sperm donors’ samples with his own are not clear at the moment, legal experts believe these revelations could unleash a potential class-action lawsuit against the former janitor.

“We cannot confirm precisely how many births have resulted from Robert Casgrains manipulations with register sperm donor specimens before proper DNA analysis is performed” warned Detective Sergeant Rod Patterson of the Toronto Police Service.

Detective Sergeant Rod Patterson of the Toronto Police Service warned that “even though the precise numbers are not known”, Robert Casgrain’s sperm “may have given birth to thousands of children over a 20 year period” he said during a press conference.

“He kept bragging that half of the clinic’s babies were his,” one former coworker told reporters when reached by phone.

Administrators at the fertility clinic were warned by employees of Casgrain’s erratic behavior and installed hidden cameras in the embryology laboratory last month before eventually contacting the police.

According to one employee who witnessed the surveillance footage, Casgrain is seen emptying the vials of semen into a sink and filling one up with his own sperm while masturbating to pornographic material.

Although it is impossible at the moment to know how many births resulted of Robert Casgrain’s manipulations at the embryology laboratory, DNA tests performed on clinical samples over the next year should authenticate which specimens are from Casgrain.

Legal experts believe Casgrain could face a sentence as low as 18 months and up to three to five years in prison according to current Canadian laws.