TUCSON, Ariz. -- A nearly yearlong investigation into dog fighting has led to the seizure of 150 dogs in what sheriff's deputies called one of the largest fight-dog breeding operations in the nation.

Pima County Sheriff's SWAT deputies said they arrested three people and detained six others in raids at four locations Tuesday morning, Pima County Sheriff Clarence Dupnik said.

VIDEO: 3 Arrested In Connection With Massive Dog Fighting Ring

Deputies, armed with warrants, were acting on information they received from the Humane Society in March 2007 that a possible dogfighting ring existed in the Tucson area, Dupnik said.

He also said the Chicago Police Department helped in the operation. "They had one of their officers stop a van that had some animals in it," the sheriff said. "As a result of that stop, an officer noticed a Tucson link and provided us with that information."

As many as 100 dogs were found and seized from one home in Tucson, the sheriff said.

Among those arrested was Mahlon Patrick, whom investigators identified as being among the top three suspected dog fighting breeders in the country.

"We have dismantled a group of people at the upper echelon of dog fighting," said John Goodwin, a national Humane Society official in charge of animal fighting issues. "This man has been involved for decades."

Patrick has allegedly been a celebrity within animal fighting circles since the late 1960s and is the architect of several pit bull bloodlines that are cherished by dogfighters, authorities said.

Officials said one of the properties housed what appeared to be a breeding kennel and had a trailer containing 50 guns.

Also seized at the properties were tools commonly used in hard-core dogfighting operations, officials said. These include treadmills specifically modified to exercise the dogs to exhaustion, injectable substances, and break sticks used to pry apart the jaws of dogs locked in battle, authorities said.

Dupnik said nearly all the dogs were pitbulls.

He said some of those detained will probably be arrested as well in connection with the operation.

Animal fighting is a multi-million dollar criminal industry that affects hundreds of thousands of dogs nationwide, said The Humane Society of the United States.

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