SAN DIEGO — Authorities made what they called the largest cockfighting bust in U.S. history with the seizure of more than 5,000 roosters, hens and chicks from two training grounds, officials said yesterday.

Fifty people have been charged in connection with the cockfighting operation near the Mexican border, which authorities said sent many of its fighting chickens to Hawai'i and the Philippines.

Agents found 4,400 chickens Saturday at a 7-acre compound in the Otay Mesa industrial area of San Diego.

Hundreds more chickens were found at a second training ground nearby, officials said.

Other stings have resulted in more arrests but none have yielded more birds, said John Goodwin, manager of animal fighting issues at The Humane Society of the United States, which deployed its own staff on the raid along with local and federal law enforcement agents.

"This bust represents a major setback to the cockfighting industry," said Eric Sakach, a Humane Society investigator.

Fifty people were issued misdemeanor citations, punishable by up to one year in jail and a $5,000 fine, and ordered to answer to cockfighting charges in early December, said Paul Levikow, a spokesman for the San Diego County district attorney's office. If the defendants have a history of animal cruelty, they may be charged with felonies.

Another 50 people are still being sought as a result of the six-month investigation, authorities said.

About 80 percent of the birds seized have been destroyed, Levikow said.

The cockfighting operation was managed and patronized largely by Filipinos, and fights were staged in the San Diego area, Levikow said.

The Otay Mesa site was raided six years ago, and more than 2,500 birds were confiscated then. Hundreds of birds were confiscated in similar raids in northern San Diego County in the spring. The district attorney's office has filed 53 cockfighting cases in six years.

"We're not done. We've just opened the door," said Lt. Daniel DeSousa of the county Department of Animal Services.

The Associated Press and Los Angeles Times contributed to this report.