A group of volunteers from Arizona have rescued 89 abused dogs living in deplorable conditions at a Missouri puppy mill.

The dogs were brought to the Phoenix area Monday for medical treatment and future adoption.

They're being housed temporarily at a residence set up to feed, bathe and care for them.

"We couldn't do this without the help of our volunteers," said Caron Lorber, rescue director of Mixed Up Mutts.

Mistreated puppy-mill dogs with serious problems were taken to local veterinarians that partner with rescue groups.

"They have injuries and illnesses that are not met," said Laura Petersen, who volunteers for three rescue groups.

"They don't get any vet care whatsoever, and are often physically and mentally abused by puppy-mill owners," she said.

Puppy mills are commercial breeding facilities that often house up to 1,000 dogs, but few will be used for breeding purposes, Petersen said.

"The others may be killed or neglected," she said. "This is a horrific industry," Petersen said.

Joey Penniston, founder of Arizona Cocker Rescue, said breeders sell puppies to brokers, who then sell them to pet stores.

Dogs that aren't purchased by the pet stores are put up for auction, where rescue volunteers spend their own money to buy as many unwanted puppies as possible.

Those that don't sell at the auctions are killed.

Federally licensed breeders will also brutally kill unwanted puppies because they may be too skinny, the wrong color or unable to breed, activists said.

"That's the problem: They're considered livestock," Petersen said of the dogs. "(Breeders) don't view pets as we view pets."