LOS ANGELES--Federal drug agents pulled off the biggest drug haul in history--20 tons of cocaine with a street value of $20 billion--Friday at a warehouse in a quiet section of the city.

Three men were arrested and approximately $ 10 million in cash seized at the warehouse on an upscale, tree-lined street in the mostly residential community of Sylmar near the San Gabriel Mountain foothills.

The men in custody were not immediately identified but were believed to be South American.

"This seizure should put to rest any further speculation that Los Angeles is in fact the major pathway for cocaine entering the country and has in fact become a major distribution center in the United States," said Drug Enforcement Administration (DEA) spokesperson Ralph Lochridge.

However, DEA officials in Washington cautioned against drawing conclusions that the hub of cocaine entry into the country has shifted to Los Angeles.

"We are not in a position to say that there is a major shift in trends in cocaine coming into the country," said DEA spokesperson Frank Shults.

Through the third quarter of fiscal year 1989 ending June 30, a total of 18.4 tons of cocaine had been seized in Miami, compared with 2.2 tons in Los Angeles, Shults said. In fiscal 1988, Miami seized 31.7 tons of cocaine, compared with 2.06 tons in Los Angeles.

Friday's haul easily topped the previous U.S. record of more than 8,700 pounds recorded in Fort Lauderdale, Fla., in 1937, and surpassed the world record, a 12-ton seizure in Colombia, said DEA agent Phil Hartman.

Officials at the DEA and the U.S. attorney's office said they believe that more than half the cocaine distributed in the country now floods in through Los Angeles. Colombian drug groups bring the drug across the border from Mexico, and Los Angeles street gangs distribute it in more than 40 U.S. cities, they have said.

Cash seizures from the drug trade totaled more than $100 million last year in Los Angeles, topping the Miami toll for the first time. The city's Federal Reserve surplus--one way of measuring illegal money laundering--has jumped by more than 2,000 percent in five years, to $3.8 billion last year.

In Friday's seizure, authorities moved in around midnight on the building in the north San Fernando Valley, about 25 miles from down-town. Across the street from the carefully landscaped warehouse are offices for the Coca-Cola Bottling Co.

Lochridge said the DEA had been investigating and conducting "intense surveillance" for a year before moving in on the warehouse.