BOSTON -- Dozens of sick puppies were recovering Thursday and a truck driver was placed under arrest when while he was delivering a shipment of dogs to Webster.

The dogs were en route to a local pet store, police said.

Animal rescue veterinarians said the 51 pups were dehydrated and weak, crammed inside an unmarked box truck that did not have working fans. They were reportedly surrounded by flies and waste.

The officer who was called to the scene contacted Webster paramedics.

Investigators said the dogs were being delivered to Elite Puppies at 172 Main St. in Webster, a pet shop Team 5 discovered has sold dogs from puppy mills in the past.

The truck driver, John T. Clayton, 39, of Missouri, was taken into custody. Police said he told them he had left from California Monday night and the dogs had not been walked since then, according to the Worcester Telegram and Gazette.

He said he had delivered nine puppies to Laughlin Kennel in Oxford, according to the paper.

Officials believe the shipping company, Puppy Ship, is tied to at least one puppy mill.

It was unknown if all of the dogs will survive.

Worcester Telegram & Gazette reported that some puppies were taken to the Cummings School of Veterinary Medicine at Tufts University in Grafton, and the others were brought to the Webster Lake Veterinary Hospital on Thompson Road for evaluation and treatment.

The Massachusetts Society for the Prevention of Cruelty to Animals said an officer in its law enforcement department was helping in the investigation into the case, along with staff from the Animal Rescue League.