Here's an offer that a lot of drivers would have a tough time turning down: free sex after nine car washes.

Police near Kuala Lumpur, Malaysia, cracked down last week after getting wind of the unique offer from the teaming of a car wash and a massage parlor in the suburb of Sunway Mentari, the Malay Mail reports.

Nine Vietnamese women, ages 18 to 28, believed to be prostitutes were arrested.

Police learned of the unique partnership between the car wash and sex ring when they kept finding car wash loyalty cards in the pockets of alleged customers of the sex ring.

The Mail quotes Emmi Shah Fadhil, the officer in charge of the area's Crime Prevention Division, as saying: "To get the extra 'offer', customers must send their cars for washing nine times within a certain period. The 10th car wash will entitle them to free sex," said Emmi Shah.