Federal drug agents in New York and Puerto Rico yesterday arrested 42 individuals and seized a $30 million shopping center near San Juan in breaking up what they described as a major heroin distribution ring operating in the United States.

Robert M. Stutman, head of the Drug Enforcement Administration's New York office, said the organization has distributed heroin in the northeastern United States, including the Baltimore-Washington area, since 1976. He said DEA has evidence the group averaged sales of 40,000 bags of heroin -- sold for $10 to $15 each -- every week. Since 1976, that would add up to more than $200 million worth of heroin.

The heroin was brought into the mainland United States from Puerto Rico, Stutman said, where the organization's leaders invested their profits in legitimate businesses, including the $30 million Towers Plaza shopping center in Bayamon, that was seized yesterday by DEA agents. He said other seizures of property are expected in the case.

Two alleged leaders of the ring, Victor and George Torres, were arrested yesterday in Puerto Rico. DEA sources said the brothers, believed to be in their late 20s or early 30s, are widely known in Puerto Rico as successful businessmen.

Stutman said the sign over the shopping center displayed the same logo as that stamped on the plastic bags of heroin -- each containing one dosage -- that the group sold: a chess king flanked by two knights.

He said the heroin bearing that logo is known on the street as "Checkmate" and is 30 to 40 percent pure, which is about 10 times the strength of the average heroin on the street. Stutman said "Checkmate" is considered a trademark in the heroin business and that the group allowed "franchise" sales by dealers who paid $10,000 per week, in addition to their purchase price, to market the high-grade heroin.

The same group also sold heroin under such trade names as Blue Moon, Paradise, 357 and 30-30.

DEA agent Robert Strang said a group of 300 DEA agents and New York City and state police made the arrests during morning raids on 24 locations in Manhattan and the Bronx yesterday where the heroin ring was believed to conduct business. According to Stutman, agents seized paper work indicating that $170,000 in heroin was sold on Tuesday from two of those locations alone.

Strang said agents also seized 18 pounds of heroin, $500,000 in cash "and two safes crammed full of cash that we haven't had time to count yet." He said three additional searches were being conducted yesterday in Puerto Rico.

DEA financial experts were being brought in to try to trace additional financial assets of the heroin ring in the United States and on the U.S. commonwealth island so that the federal government can move to seize them, according to Strang. "We're trying to dismantle the entire organization," he said. "What we got today is probably just the tip of it."