Nearly 60 chickens were removed from an East Palo Alto property on March 23 after city police and Peninsula Humane Society officers discovered an alleged cockfighting operation -- one of the largest in the county in recent years -- and resulted in one arrest.

The operation was uncovered after East Palo Alto police initially investigated a call at 3:50 p.m. regarding an aggressive dog that was loose on the street. The animal was associated with the property where the chickens were found, according to police Chief Albert Pardini noted in a weekly crime bulletin.

Arriving officers found the dog in the rear yard of a residence in the 1200 block of Cypress Street. The dog was found not to be aggressive toward people, but it was trying to attack roosters and hens in the rear yard, according to Pardini.

Officers located 56 cocks, hens and chicks and cages constructed near the back fence, which contained most of the birds. A dead rooster was lying on top of one of the cages and officers noticed two or three injured birds in the cages. Police notified the Peninsula Humane Society, which investigates suspected animal cruelty cases.

Arriving on scene, Lead Humane Investigator Christina Hanley found evidence that immediately led her to suspect a cockfighting operation, Humane Society spokeswoman Buffy Martin Tarbox said. Dozens of the birds had been "dubbed " -- their combs, wattles and earlobes were removed -- to make them more lean for fighting and fight longer, she said. This type of modification of roosters is consistent with cockfighting.

Many of the birds still had open and bleeding wounds from the dubbing process, Hanley later said.

Police and Humane Society officers located 90 metal "slasher" knives in an open shed, which are taped to the legs of the birds to make fighting more deadly. Several vials of antibiotics used to treat injured roosters were also found in the shed, she said.

The suspect, 29-year-old Aldenni de Jesus Trujillo Santiago, agreed to surrender the chickens. All 56 birds were determined to be either severely injured or bred to be too aggressive for adoption and were euthanized, Tarbox said.

Trujillo Santiago was booked into the Maguire Correctional Facility in Redwood City on felony crimes against animals and two misdemeanors of possession of fighting birds. The San Mateo County Sheriff's Office said a booking photo was not yet available. Humane Society officials are continuing their investigation.

"Cockfighting is animal abuse and is highly illegal. The Peninsula Humane Society and SPCA deals with cockfighting cases every two to three years, although not necessarily involving the number of birds associated with this recent case. We respond to reports of animal cruelty, including cockfighting and last year alone our humane investigators handled more than 450 cases of animal cruelty and neglect," Tarbox said in a statement to the Palo Alto Weekly.

San Mateo District Attorney Steve Wagstaffe said the case had not yet reached his office. He expressed surprise at the size of the seizure. In recent years his office has not received many cases, perhaps one a year to every three years.

"The numbers (of birds) we see are five, 15, 20. This would be a large operation," he said.

Trujillo Santiago had only one prior prosecution, in June 2013, for a state Fish and Game violation of fishing without a license and later convicted, Wagstaffe said.

Pardini said in addition to confiscating the birds, a City of East Palo Alto Code Enforcement team responded to inspect the yard and found several violations, including two illegal outbuildings, illegal wiring and a potential illegal addition to the home. The tenants were issued a warning to correct all violations, remove the bird cages and to remove two inoperable vehicles from the front yard. The code enforcement team will conduct a follow-up visit at the residence to insure all violations have been corrected, he said.

Tarbox said the Humane Society has a Cruelty Hot Line and encourages the public to call if they suspect an animal is being abused. The number is 650-340-7022, ext. 601.