Janesville Police are warning residents about a scam involving Facebook.
Detective Chris Buescher says two teen girls received messages on the social networking site, asking if they wanted to make "easy, legit money."
Buescher says the girls were directed to buy $100 prepaid Visa cards, and provide the numbers, so the acquaintance could change the balance and make it $1000.
When the girls checkout out how much money they had left on the cards, there was nothing left.
Police say anyone receiving similar messages should delete them, and report the incident to authorities.