As many as 400 dogs were seized and about 30 people arrested during raids in five states Wednesday that animal welfare groups are calling the largest simultaneous raid of dogfighting operations in the U.S. On Thursday, investigators seized dogs in Nebraska.

U.S. attorneys in four of the states announced related indictments accusing 26 people of cruelties ranging from denying animals medical treatment to shooting dogs in the head when they didn't fight well, then throwing their carcasses into a river or burning them in a barrel.

The Nebraska Humane Society seized four dogs Thursday as part of the largest dog fighting sting in U.S. history.

"Law enforcement officers served a search warrant at two properties in Tecumseh, including a field with the wooded area. They seized four pit bull mix dogs," said Johnson County Attorney Julie Smith Hogancamp.

Thursday night, investigators served two search warrants in Tecumseh, Nebraska, in connection with the federal indictment of resident Julio Reyes on the charge of dog-fighting. Authorities say the dogs belong to 28, of Tecumseh. Reyes was federally indicted Wednesday on allegations that he is part of a dogfighting ring out of Northwestern Missouri.

"We received information from the Brown county attorney which led us to assist them in writing search warrants for two locations in Tecumseh, Nebraska," said Mark Langan with the Nebraska Humane Society in Omaha.

"There were two pitbull mix dogs seized from each location, as well as some other various items which the investigators described as potential animal fighting paraphernalia," Hogancamp said.

Kathy Warnick, president of the Humane Society of Missouri, said tips had come in from "multiple sources" about dogfighting, and anti-cruelty workers worked with federal authorities for 18 months.

"This heinous, heinous bloodsport is not going to be tolerated," she said.

The Humane Society took two dogs from kennels in Reyes' backyard. The other two were found chained up in a wooded area belonging to another man whose property Reyes frequents.

"The dogs are in fairly good condition," said Langan. "At least two of them have old fight scars around their face area, leg area. They appear to be somewhat old in nature, however, they dogs are only one to two years old so that show that they were at least recently fought within the last year."

While the dogs appear to have been fought, authorities are not blaming Reyes just yet.

"We don't know at this time whether we're going to charge Mr. Reyes with anything," Hogancamp said.

And the fate of the dogs is similar. The Humane Society in Omaha will keep them as long as Reyes' case remains open, but it's unclear what could happen to them once the case closes.

Task forces of federal, state and local law enforcement agencies conducted the raids and made arrests in Missouri, Illinois, Iowa, Texas and Oklahoma following a more than year-long investigation prompted by information gathered by the Humane Society of Missouri. It wasn't clear whether or to what extent the operations were related.

Seven people from Missouri, Iowa and Nebraska were indicted by the U.S. Attorney's office in western Missouri. The indictment said the seven acquired, bred and trained pit bull dogs for fighting and denied medical treatment for wounds and injuries. One man used a .22-caliber rifle to shoot and kill two under performing dogs who fought in roll fights, shot each animal twice in the head, then placed the carcasses in plastic containers outside a garage, according to the indictment.

The national Humane Society said there also were arrests in Arkansas associated with dogfighting, but no dogs were seized.

Dogfighting is banned throughout the United States and is a felony in 50 states. A law enacted two years ago increased penalties for activities that promote or encourage animal fighting after a long campaign by animal-welfare groups.

Wayne Pacelle, president and chief executive officer of the Humane Society of the United States, said dogfighting operations typically are not small acts of animal cruelty, but part of organized criminal networks.

"This was quite an operation and marks the latest in a series of actions that are driving dogfighting, we hope, off the cliff," Pacelle said.

The Humane Society of Missouri is sheltering more than 300 dogs -- believed to be mostly pit bull terriers -- seized in Missouri and Illinois raids and their conditions are being assessed. The dogs will be housed, cared for and evaluated at an undisclosed emergency shelter in St. Louis.

HSUS spokeswoman Jordan Crump, a spokesman with the Humane Society of the United States, said each dog seized in all the raids will be evaluated by behavioral experts in hopes of placing as many as possible in adoptive homes. The same happened for the dogs seized from Michael Vick's Bad Newz Kennels in the former Atlanta Falcons quarterback's dogfighting case. Animal welfare groups said most were able to be placed in homes or sent to an animal sanctuary.

"The Vick case taught us to see dogs in these cases as victims," said Donna Reynolds, with the Oakland, Calif.-based pit bull rescue and education group Bay Area Doglovers Responsible About Pit bulls, or BAD RAP.

"Animal welfare organizations will have to come together to ensure animals are comfortable in their confinement and they have the best opportunity to be evaluated, and if possible, offered rescue resources," Reynolds said.

The U.S. Attorney's office in St. Louis said five men were indicted there for allegedly running kennel operations to buy, breed, train, condition and develop pit bulls for fighting ventures under such names as Ozark Hillbillys Kennel, Cannibal Kennel and Hard Goodbye Kennel. The men routinely abandoned, destroyed and disposed of pit bull terriers that lost fighting competitions, did not perform aggressively, or became injured or disabled while fighting, the St. Louis indictment said.

The U.S. Attorney's office in eastern Texas said nine people were indicted June 30 on dogfighting charges there. Two FBI task force officers working with a confidential informant posed as dog owners and attended fights in Texas and Oklahoma, according to the indictment. They managed to get video and audio from Jan. 17 fights near Tahlequah, Okla., by accompanying suspects to a remote country building for three dogfights, the indictment said.

Authorities said one man was indicted in Oklahoma and arrested Wednesday near Welling in rural Cherokee County. Five people indicted in southern Illinois for dogfighting in St. Clair and Madison counties also were arrested Wednesday.