Citi Bike says it is aware of a scam in New York City in which thieves are switching the QR code stickers on rental bicycles in order to steal bikes unwittingly unlocked by customers.

The scammers wait for a renter to unlock a bicycle using the QR code, then ride away on the bike to which the code actually belongs, officials said.

�Citi Bike is aware of this issue and, while it has not been widespread, we have been actively working to address it in a number of ways, including upgraded QR decals,� said Citi Bike spokesperson Jordan Levine told The New York Post.

Each rental ride costs $3. But a customer can be charged $1,200 if a bicycle they rent ends up lost or stolen.

June and July were two of the busiest months in the history of the program, with a total of more than 6.2 million rides purchased in New York City, including a single-day high of 126,099 rides on July 24 alone, Levine said.

(AP)