Animal activists say more than 200 dogs are being kept in deplorable conditions at Sportsman's Kennels in Manorville.
Humane World for Animals sent an undercover investigator to work at Sportsman's Kennels for two months after it was tipped off by community concerns.
It says that an investigator found roaches in the pet food, sick puppies and dogs kept together in small plastic bins.
"Our investigator found just horrible conditions, I refer to it as decrepit conditions," said Brian Shapiro, with Humane World for Animals. "Animals that are matted, showing signs of having some blood on them."
The global nonprofit says this American Kennel Club-linked breeder is one of the most egregious puppy mills in the United States.
Pet parents, like Laura Warner, from Manorville, say they're disturbed by the findings.
"It does seem like too many dogs to be held in that facility so that doesn't really surprise me that something might be taking place that's not healthy for the dogs," she said.
No one answered the door at Sportsman's Kennels, and when News 12 called, the person who answered the phone said, "Have a nice day" and hung up.
Humane World for Animals says it shared its findings with the State Attorney General's Office and the Suffolk County District Attorney's Office.
"This isn't over. We're going to be keeping an eye on Sportsman's Kennels," Shapiro said.
The Suffolk District Attorney's Office says it is not confirming or denying that it is launching an investigation.
News 12 reached out to the State Attorney General's Office and the American Kennel Club for comment about the allegations against Sportsman's Kennels and is waiting to hear back.