By Jonathan Kaminsky

OLYMPIA, Washington (Reuters) - Washington state authorities have euthanized scores of steroid-filled roosters after raiding a farm and arresting a man on suspicion of raising the birds for cockfighting, prosecutors said on Tuesday.

Victor Hugo Gallegos Chavez, 35, the lone defendant in the case, was arrested at his home in Rochester, about 70 miles southwest of Seattle by authorities acting on a search warrant on Monday.

Court documents filed by prosecutors cite Chavez and others as saying he sold the roosters to fight in Mexico, Portland, Oregon, and elsewhere.

Cockfighting is outlawed in all 50 U.S. states but remains legal in Mexico, among other countries.

Some 240 roosters and 60 hens seized in the raid were euthanized after Chavez's arrest, said Thurston County Senior Deputy Prosecuting Attorney Joseph Wheeler, adding that the steroids rendered the birds unsuitable for rehabilitation or human consumption.

"I love chickens. I have chickens of my own," Wheeler said. "To treat a bird as a toy is something that is not right in the universe."

At Chavez's initial court appearance on Tuesday, a judge found evidence of probable cause for 100 counts of animal cruelty, one count of illegal gambling and one count of animal fighting, Wheeler said. All are felonies punishable by up to five years in prison and a $10,000 fine.

Chavez, who is being held in lieu of $25,000 bail, will be formally charged later this week, Wheeler said.

The case against Chavez was built during a two-year investigation by the Washington State Gambling Commission, Wheeler said. The probe included the use of hidden cameras that recorded events at the farm.

Gambling Commission agents observed Chavez keeping the birds tethered to barrels, taunting them and prodding them to fight for up to a minute at a time.

Federal immigration officials have a placed a hold on the case, meaning there is evidence that Chavez is in the United States illegally, Wheeler said. But Chavez will face the charges to be filed against him before any possibility of his being deported, the prosecutor added.

(Reporting by Jonathan Kaminsky; Editing by Steve Gorman and Eric Walsh)