Startled women have returned to their cars in Melbourne's north-east to find anonymous "love" notes taped to their windscreens, signed with: "Your Secret Admirer" and a contact email.

The Epping Sexual Offences and Child Abuse Investigation Team launched an investigation into the handwritten notes - which compliment women on their beauty - after police found a Facebook thread discussing the letters on a local community page.

Police have since spoken to a 29-year-old man in relation to the matter.

Detective Senior Constable Graeme Wassell said police first became aware of the notes a few months ago, and had been attempting to build a case against the suspect since.

"Witnesses have identified a female that has had ongoing contact with the suspect through social media, however, without an official complaint from this individual, police have been unable to act on that charge," he told Fairfax Media.