BANGOR – State animal welfare officials are expected to seek permanent custody today of more than 20 dogs, mostly puppies, seized late last week as part of an 18-month investigation into illegal dog sales in the Bangor area.

At least four people have been identified, but their names not released, by authorities as being involved in the sale of the small, mixed-breed dogs, many of which suffered from illnesses that put not only the animals at risk, but also human beings.

“It’s not one of our more common investigations,” Norma Worley, director of the state Animal Welfare Program, said Tuesday.

The illegal, unlicensed sale of the puppies has been under investigation for a year and a half and recently brought together a half dozen agencies working cooperatively to execute four simultaneous search warrants on June 2.

Two homes in Bangor were searched as were a home in Glenburn and one in Orono.

Authorities are still unraveling how big this case is, including how many dogs were sold and how many others were involved.

“This is an overwhelming case,” said Penobscot County Assistant District Attorney James Diehl whose office may ultimately pursue criminal charges.

In the more immediate future, the state is expected to file a motion today in 3rd District Court in Bangor for permanent custody of the 23 dogs, one of which was purchased by undercover state officials last week.

The puppies for sale included Labrador retriever and beagle mix and Yorkshire terrier and poodle mix.

Some of the puppies were too young to be sold, and many were sick, carrying a zoonotic disease, which can be passed on to other dogs as well as human beings, Worley said.

Orono police Sgt. Josh Ewing was part of the contingent of more than a dozen officers and agents who executed the search warrants. While carrying out puppies, he noted some looked sick, the officer said Tuesday. Ewing said he wore rubber gloves to limit his exposure, and he said he could feel the puppies’ ribs and their stomachs were distended.

The sick dogs were treated Friday and during the weekend at the Brewer Veterinary Clinic, where they were given medication and later released to the Bangor Humane Society, Worley said.

“Without this medication, it’s very likely a good percentage would not have made it,” she said. The disease is spread through feces and can be transmitted to humans. Particularly at risk are the young, old and those with compromised immune systems, she said.

Officials are concerned about animals that have been sold previously.

“They’ve been selling for 18 months to two years, and they’ve sold a lot of puppies,” Worley said.

The state’s animal welfare agency received more than a dozen complaints about the illegal and roving pet shop, including complaints that purchased puppies became ill or died a short time after purchase, she said.

Buyers, responding to newspaper advertisements, met the dog sellers at locations and were sold the puppies from motor vehicles, including from the back of pickup trucks. Puppies were sold for between $200 to close to $500, according to Worley.

State animal welfare officials used the Maine Drug Enforcement Agency to both help monitor the illegal activities and also to draft the search warrants, Darrell Crandall, a division commander with the MDEA, said Tuesday.

An MDEA agent, who also works with the Penobscot County Sheriff’s Office, went undercover with a state animal welfare agent to purchase a dog last week.