Over 20 people have been arrested in a horrific dog-fighting ring that spanned several states and involved at least 130 dogs, including puppies, WBAL-TV reported.

Maryland investigators busted 22 suspects as part of a year-long investigation that recovered 139 dogs that were abused, forced to breed and injected with steroids in the Baltimore-based operation, the Office of the State's Attorney for Baltimore City said Monday. Dog-fighting rings were also uncovered in North Carolina and West Virginia.

According to charging documents obtained by the news station, investigators found breaking sticks, steroids, chains and conditioning harnesses allegedly used by the suspects from April 2013 until this year. Dogs used for fighting are often forced to wear the chains and are subjected to the sticks and harnesses in an attempt to make them more violent, WBAL-TV reported.

Dog-fighting rings covered in blood and several breeding stands, used to breed the animals, were also recovered from the defendants. The fighters called the breeding stands "rape stands," according to the court documents. They also allegedly administered medical treatment to wounded dogs to avoid suspicion from veterinarians.

Dog-fighting, which is illegal, involves hundreds of thousands of dollars in bets placed on the animals and often operates across state borders. The facilitators themselves are usually associated with the illegal dealing of firearms and drugs, both of which were also seized in the investigation.

"The firearms and narcotics seized during the course of this investigation...establish that there is a strong connection between those individuals who would subject animals to horrific treatment and abuse and those engaged in the drug trade and acts of violence," State Attorney Gregg Bernstein said according to WBAL-TV.

The indictment "highlights this connection and hopefully will protect innocent and vulnerable animals from further abuse and reduce violent criminal activity that adversely impacts our community," he continued.

Many of the suspects, ranging from age 29 to 76, have previous criminal records, including one who was convicted for murder.

Charges against them include dog-fighting conspiracy, aggravated cruelty related to dog-fighting and animal abuse and neglect.