ELBERT COUNTY, Colo. -- Every once in a while the underground world of cockfighting is exposed, especially when the roosters are delivered via the U.S. Postal Service.

Mauro Loera-Leuvanos, 39, was arrested recently on cockfighting charges after post office employees in Parker said they were getting three suspicious shipments a week, all to the same person.

They said their suspicions were confirmed when they saw "American Fighting Fowl" printed on the boxes.

"Oh, it crows all the time, and when you have two together, roosters don't like each other, so I think they're trying to outcrow each other and it's pretty noisy," said John Wikler with the U.S. Postal Service.

Police followed the owner to his home in Elbert County where officers served a search warrant. More than 20 birds were found.

An arrest affidavit showed the owner claimed, "They were used for eggs." However, investigators said they found several roosters that had been surgically altered for fighting, their combs removed and spurs cut off. Police arrested the man on felony animal fighting charges. The Elbert County Sheriff's Office said the birds were bred for fighting and have all been euthanized.

"Hopefully it will send a message to everybody else that wants to do this that it's not acceptable and it's not lawful to do it," said Elbert County Sheriff's Office spokesman Jim Underwood.

Colorado has some of the toughest cockfighting laws. It's a felony to even watch a fight in this state. However, law enforcement said the recent arrests show that's just forced the fans further underground.

"So, it's just growing out here. It's not a surprise because it's so rural, it's a lot easier to hide it," said Underwood.

The state's veterinarian's office has assisted in at least four busts this summer. Investigators said they do not know where the fights are actually taking place.