INDIANAPOLIS — Drivers in Indiana and Kentucky could be blocked from renewing their vehicle registrations over unpaid Ohio River bridge tolls.

Officials said Tuesday that a hold will be placed on vehicle registrations if a toll goes without payment after at least four notices have been sent. They say full payment is required for a hold to be released.

Scott Adams of the Indiana Department of Transportation says both states will start cracking down later this month.

Tolls began Dec. 30 on three bridges connecting Louisville, Kentucky, and southern Indiana. Officials say more than $50 million of tolls have been collected since. Daily traffic reached more than 80,000 vehicles in September.

RiverLink is the all-electronic toll network that uses cameras to capture drivers’ license plates so drivers can be billed.