A Richmond Hill, Ont., man faces charges after police allege that he had unprotected sex with a minor, while knowing that he was HIV positive.

York Regional Police say they began investigating allegations in February that a man had assaulted a woman with a weapon and threatened to kill her.

Further investigation led police to determine that back in October 2011, the same man had been diagnosed as being HIV positive at the time and "knowingly engaged in unprotected sex with a minor and subsequently infected the minor with the disease."

Roman Krouglov

York Regional Police released this image of Roman Krouglov, 26, of Richmond Hill, Ont., on April 2, 2014. (York Regional Police)

Roman Krouglov, 26, faces charges of sexual interference, aggravated sexual assault, assault, assault with a weapon and uttering death threats.

Police say that the accused was arrested on Feb. 12. He has been held in custody and is due to appear in court Thursday.

Police are concerned there may be more alleged victims.

According to police, Krouglov solicited sex through online classified ads, using an email address of romankrouglov@gmail.com. The ads requested "casual encounters," police say.

Anyone with information is asked to contact investigators at 1-866-876-5423, ext. 7241, or to call Crime Stoppers at 1-800-222-TIPS.

With files from The Canadian Press