The Border Patrol seized 4,391 pounds of cocaine, the largest haul in the agency's history, after a fiery gun battle with smugglers in a caravan of about 40 horses near the Mexico border, officials said Thursday.

The U.S. Drug Enforcement Administration estimated the value of the cocaine at $199.7 million.Border Patrol agents and the smugglers - about a dozen in all - exchanged gunfire before they fled into Mexico, said Jacqui Parker, a spokeswoman for the Border Patrol's Tucson office. No one was injured.

The Border Patrol's previous record cocaine seizure was 3,297 pounds found in a travel trailer near the Arizona border town of Naco in the summer of 1989.

Parker said two agents on patrol near the Mariposa Gate, a crossing for commercial trucks about one-half mile west of Nogales, encountered the caravan of about 40 horses just after 10 p.m. Wednesday.

The smugglers opened fire with high-powered rifles and the agents returned fire, Parker said.

The smugglers continued firing in an attempt to overrun the agents' position but fled, abandoning the packhorses, when about eight or nine backup agents and a number of other local law enforcement officers arrived.

The cocaine was packed in burlap sacks, each containing about 100 pounds of the drug, Parker said. It was believed the cocaine may have originated in Colombia.

Parker said drug smugglers on horseback are common along the Arizona border "because of the rugged and remote hilly terrain."

"We've been fighting horsepack trains for years, but 40 horses at one time, we've never seen the like of that," Parker said.

She said the DEA would check the cocaine to determine whether it carried the markings of any organization known to authorities.

The cocaine probably was headed for Tucson or Phoenix for distribution throughout the United States, Parker said.

Immigration and Naturalization Service Western Regional Commissioner Ben Davidian said the bust points up "the incredible dangers facing Border Patrol agents on a daily basis."

"The officers . . . showed the type of raw courage that we have come to expect from the men and women on the front line, defending our nation's borders," he said.