More than a dozen manhole covers have been stolen in Hartsville, Darlington and Lamar in recent days, according to police.
Officers believe thieves are taking the covers and selling them to shred mills.
They say one cover weighs as much as 200 pounds, so it takes a lot of muscle to walk off with one.
"You know, it takes some time to lift those things and put them in the trunk of a car or the bed of a truck. Right now, we're working very hard to find out who's taking them and where they're taking them to," said Hartsville Police Chief James Hudson.
It costs about $400 to replace a manhole cover.
Police say they're checking with scrap yards to see who's cashing in on the thefts.
"If I had to say, it would probably be because they were melting them down or somehow taking them and selling them for money," Chief Hudson said.
Darlington police say they've had at least one incident where someone has taken the crate cover off of a drainage system.
Officers are working together to solve the crimes.