Cat owners in Denver, Colorado have been warned to keep their pets at home after a number of mutilated cats were found dead in the area.
Many of the cats were decapitated or had their organs removed
The eviscerated remains of four cats were found over the weekend, heightening fears that a cat killer may be on the loose.
The authorities say around 40 mutilated cats have been found in the Denver area over the past year.
There have been a string of similar cases in Salt Lake City, Utah, where 11 cats have been found been found mutilated - many with their heads or organs missing.
In the majority of cases in Denver the cats have been sliced open, often with surgical precision, and their internal organs removed.
We have to start asking ourselves if this person is capable of doing this to a human victim. Maybe they're desensitising themselves with cats
Temma Martin, Salt Lake County Animal Services
According to the Associated Press in several cases the killer seems keen to taunt the cats' owners by dumping the remains outside the homes.
Christy Hughes, whose 15-year-old cat, Bugsy was killed, told Associated Press that her husband found the eviscerated body of their pet outside the front door of their home in the area of Aurora two weeks ago.
The cat was attacked sometime between 0100 when he last went out, and 0615, when he was found dead.
Mrs Hughes said she felt guilty because she had stopped reading news stories about the attacks, which began in July 2002.
"I blame myself because had I read it, I never would have let my cat outside," she told the Associated Press. "I've had a hard time forgiving myself for that."
Serial killers like Jeffrey Dahmer are known to have attacked animals
She said that she had been traumatised by the experience: "For a week I couldn't sleep because I just kept seeing my cat over and over. It breaks my heart seeing other people go through this."
United Press International reported that a task force of animal control officers, police and members of The Denver Dumb Friends League, which has offered a $12,000 reward for information leading to an arrest, are investigating the attacks.
The Colorado penalty for aggravated cruelty to animals is up to 18 months in jail and a $100,000 fine.
However, experts are concerned that the attacks also point to disturbing behaviour that may escalate.
According to criminologists one of the key childhood symptoms displayed by adult serial killers is animal mutilation.
"We have to start asking ourselves if this person is capable of doing this to a human victim. Maybe they're desensitising themselves with cats," said Temma Martin, spokeswoman for Salt Lake County Animal Services.
In the meantime the authorities in both Salt Lake City and Denver are asking cat owners to keep their pets indoors, advice which some owners are failing to heed.
"Some people argue their animals do not like being kept inside. But, look at the stakes here," said Ms Martin.