CHICAGO (AFP) — More than 350 dogs — most of them pit bulls — were rescued Wednesday in what officials said was the largest dog fighting crackdown in US history.

Authorities in six states seized the dogs in coordinated raids which netted the arrests of 26 people accused of forcing the dogs to fight to the death and “routinely and inhumanely” killing them if the dogs were injured too badly to fight again.

Each count of conspiracy to promote and participate in dog fights carries a maximum penalty of five years in jail and a fine of up to 250,000 dollars.

An indictment unsealed against seven of the defendants charges that two dogs were shot in the head and dumped in plastic containers outside the garage where a fight was held because they “did not perform to the handler’s/owner’s expectations.”

Others were shot and then tossed into a river or burned in a barrel, officials said.

Organized dog fighting is illegal in the United States, but the Humane Society estimates that some 25,000 dogs are forced to fight for profit every year.

The animal welfare organization estimates that 40,000 people follow the underground dog fighting circuits and another 100,000 meet in neighborhood streets, alleys and hideaways.

“Dog fighting inflicts serious injuries and death upon dogs that are bred and trained to be dangerously aggressive,” Matt Whitworth, acting US Attorney for the Western District of Missouri, said in a statement.

“Like many dog owners, I am appalled that such a cruel and inhumane activity occurs in our state. We will vigorously prosecute those who illegally practice this so-called sport.”

The operation stemmed from a tip from the Humane Society of Missouri, which has set up a temporary shelter in St. Louis to care for many of the dogs.

“We are committed to giving dogs who have come from such horrible abuse the absolute best chance for a good life,” said Debbie Hill, director of the temporary shelter.

“It is a tragedy that because of mistreatment by humans for financial gain and so-called sport, many dogs used in animal fighting may not ever be able to be placed in a home situation.”