TULSA, Oklahoma - The Humane Society of the United States says Oklahoma is one of the worst states in the country when it comes to puppy mills.

It’s now making a statement along Oklahoma's highways with a new billboard campaign encouraging drivers to report illegal puppy mills.

Three years ago, volunteers saved more than 100 dogs from miserable conditions inside a puppy mill in Sand Springs, but animal rescues say it was only one of many more illegal breeding operations across the state.

"We call it a dog factory - where greed overcomes the owners and it's not about the health or welfare of the animal. It's about how much money they can make, how much profit they can make," said Jamee Suarez with the Oklahoma Alliance for Animals.

That's why, right next to I-44 headed east toward Catoosa, you'll see a banner asking drivers to call in any tips they might have about illegal puppy mills for a $5,000 reward.

"Billboards are high; somebody sees it, they're going to say, 'Hey, there's some reward money out there, let's give them some information,’" Suarez said.

The Humane Society of the United States says Oklahoma is one of the top five worst states for illegal breeding operations.

But because puppy mills are typically in rural areas, they're hard to track down.

Suarez said, "They're kind of hard to find, 'cause they're hidden," said Suarez.

The group is asking for the public's help, saying it could be the difference that saves an Oklahoma animal from a sad fate.

"The cages are usually filthy that they keep them in; they keep a female breeding dog until she can breed no longer, and then they will kill her," said Suarez.

To report information regarding an illegal breeding operation, call 1-877-MILL-TIP or visit their website.