GOLD RIVER - Fish and Wildlife officials want to know who's responsible for leaving threatening messages and poison in an effort to kill cats on state property.

A woman trying to help the cats found the poison Friday night, days after someone left a a warning letter demanding she stop her rescue efforts. It happened along the banks of the American River next to the Nimbus Fish Hatchery.

A big problem along the American River comes from people abandoning their cats. That's led to a large feral population which the Department of Fish and Wildlife is trying to control humanely.

Michelle Lee admits she's a cat lover, so when she saw large numbers of feral cats along the American River, she wanted to do something to help them. She contacted Animal Control and the Department of Fish and Wildlife, and they agreed to work with her.

"Animal Control will use live capture traps, and what that allows us to do is it takes the animals out of here safely, spay or neuter them, and we often release them because after a certain period of time, they're not adoptable," Department of Fish and Wildlife Scientific Aide Jason Fareira said.

Lee set traps not just for the adult cats, but also kittens she believed could still be adoptable.

"What she's doing is definitely helping the population stay at as low a number possible is what we're after," Fareira said.

But on Tuesday, when Lee came back to the river, she found all her traps gone, replaced with a sign that read, "All feral cats will be trapped, shot or poisoned. You like em, take em to your house. They have no place here."

"There's just no reason for that," Fareira said. "There's good people out here trying to do a good thing for, not just the cats, but for the other wildlife and the visitors here."

"You know this is a very hateful sign," Lee said. "I just wonder what kind of a mind would do this."

The threats didn't deter Lee and she kept coming back. On Friday night, she found that one of the bowls she had used to bait the traps was filled it with rat poison.

"And when we got here there were four to six kittens eating out of the bowl," Lee said.

"That kind of behavior is completely intolerable for a public park," Fareira insisted.

Fish and Wildlife officials said the land, which is state property, falls under their jurisdiction, and no one has any business taking it upon themselves to try to control the feral population, certainly not with poison.

"What happens when a child sees it, picks it up, handles it?" Fareira said. "You could be potentially harming someone's child."

Lee was able to rescue three kittens, and law enforcement will be on the lookout for whoever is responsible for leaving the poison.

Rescuers said the three kittens rescued are thriving and should be adoptable in the days ahead.