No charges have been filed in the case, but Surry County Commonwealth's Attorney Gerald Poindexter said Wednesday as many as six to 10 people could be involved.
Dog fighting is a felony in Virginia.
"I'm convinced from what I saw that dog fighting has occurred down there, but who was involved in it I don't know at this point," Poindexter said in a telephone interview, noting that he saw what looked like blood spatters in a room over a garage.
"We're going to find out."
The Atlanta Falcons quarterback has blamed relatives for taking advantage of his generosity and insisted he's rarely at the house - even though he was the owner.
Last week, the Daily Press of Newport News reported Vick has sold the house.
The people possibly involved include those who have lived or been on the premises and people who took care of the dogs and the property, Poindexter said.
He said what looked like blood splatters on the floor of a room over a garage were the "most suggestive evidence of dog fighting. There were blood splatters, and somebody would have to explain to me how you draw blood in the normal training of pit bulls."
He also said he was told there was a carpet with blood stains on it rolled up in a corner of a room downstairs, but he did not see that. Poindexter said he and Surry County Sheriff Harold Brown called a meeting Monday with investigators from the State Police and animal control to summarize evidence and examine reports. He said he doubted the review would be finished in time to submit to a grand jury scheduled to convene Tuesday.
"I am not defending Mr. Vick at all, but I don't want to see us rush into a case prematurely," he said. "We are in the process of collecting evidence as best we can."
"It includes analyzing forensic evidence. It's not traditional. You can't go to the state sources that we usually have to do analysis of dog blood." After the meeting, Poindexter said he and Brown will "try to decide where we're going. If it's necessary to call a special grand jury, we'll do that." Brown did not immediately return a telephone message seeking comment. He was said to be out of the office Wednesday afternoon. The case began in late April, when police conducting a drug investigation raided the house in rural Surry County and found dozens of dogs. They also found items associated with dog fighting, including a "pry bar" used to pry apart a dog's jaws. Poindexter said the county seized some 60 dogs from the house. Several dogs had old scars, but by and large, the dogs appeared to be well-cared for, he said. Vick is a registered breeder, so "the mere fact that he had a lot of dogs doesn't mean a whole lot," Poindexter said. "If he's implicated in any way - and I'm not saying he isn't, I would think that he is - there are about 10 other people who, from what we know, have a much more regular contact with the property and the animals," the prosecutor said. Vick has said he let a cousin, Davon Boddie, live at the house, and that he didn't know a large kennel on the property could be involved in a criminal activity.